DOCSLIB.ORG

The Diurnal Cycle of Outgoing Longwave Radiation from Earth Radiation Budget Experiment Measurements

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
The Diurnal Cycle of Outgoing Longwave Radiation from Earth Radiation Budget Experiment Measurements VOL. 60, NO.13 JOURNAL OF THE ATMOSPHERIC SCIENCES 1JULY 2003 The Diurnal Cycle of Outgoing Longwave Radiation from Earth Radiation Budget Experiment Measurements G. LOUIS SMITH Virginia Polytechnic Institute and State University, Blacksburg, Virginia DAVID A. RUTAN Analytical Services and Materials, Inc., Hampton, Virginia (Manuscript received 8 April 2002, in ®nal form 23 January 2003) ABSTRACT The diurnal cycle of outgoing longwave radiation (OLR) from the earth is analyzed by decomposing satellite observations into a set of empirical orthogonal functions (EOFs). The observations are from the Earth Radiation Budget Experiment (ERBE) scanning radiometer aboard the Earth Radiation Budget Satellite, which had a precessing orbit with 578 inclination. The diurnal cycles of land and ocean differ considerably. The ®rst EOF for land accounts for 73% to 85% of the variance, whereas the ®rst EOF for ocean accounts for only 16% to 20% of the variance, depending on season. The diurnal cycle for land is surprisingly symmetric about local noon for the ®rst EOF, which is approximately a half-sine during day and ¯at at night. The second EOF describes lead±lag effects due to surface heating and cloud formation. For the ocean, the ®rst EOF and second EOF are similar to that of land, except for spring, when the ®rst ocean EOF is a semidiurnal cycle and the second ocean EOF is the half-sine. The ®rst EOF for land has a daytime peak of about 50 W m22, whereas the ®rst ocean EOF peaks at about 25 W m22. The geographical and seasonal patterns of OLR diurnal cycle provide insights into the interaction of radiation with the atmosphere and surface and are useful for validating and upgrading circulation models. 1. Introduction the surface and atmosphere due to temperature, cloud, The diurnal and annual cycles of solar irradiance are and humidity variations during the day. These daily var- the two major forcing cycles for our weather and climate iations may be divided into diurnal variations, which system. The outgoing longwave radiation (OLR) re- repeat periodically, and transient variations due to sponds to this forcing by varying on both an annual and weather events, which do not repeat on a daily cycle. daily basis as a function of time and location. The ®rst Accurate knowledge of the diurnal cycle is crucial for satellite measurements relating to the diurnal variation several reasons. For sun-synchronous satellites, knowl- of OLR were analyzed by Raschke and Bandeen (1970). edge of the diurnal cycle is required to use radiometer Their data, from a sun-synchronous spacecraft, only al- measurements to compute radiant earth energy budget lowed computation of near-noon and midnight differ- (Brooks et al. 1986; Barkstrom and Smith 1986). Given ences of OLR. Nevertheless, they demonstrated the var- that one has measurements at only a few local times for iation of OLR with local time. In this paper we examine any given region, to compute daily average OLR, it is the diurnal cycle of OLR by use of 5 yr of data from necessary to make assumptions about variations of OLR the Earth Radiation Budget Experiment (ERBE) scan- across the day. A primary objective of the dedicated ning radiometer which was aboard the Earth Radiation ERBS was to de®ne these diurnal variations over the Budget Satellite (ERBS). This spacecraft, with an in- earth so that measurements from instruments in sun- clination of 578, precessed through all local times every synchronous orbits could be better interpreted. This ob- 72 days. The ERBS radiometers provided broadband jective resulted in the orbit design for ERBS by Harrison measurements of OLR and re¯ected solar radiation, and et al. (1983). Too, the ability of circulation models to the data are uniquely suited for study of the diurnal simulate the diurnal cycle of OLR depends on how well cycle of OLR. surface and atmospheric interactions are modeled. Ob- Daily variability of OLR results from interactions of servational knowledge of the diurnal cycle of OLR pro- vides an excellent method for validation of these mod- Corresponding author address: G. Louis Smith, Mail Stop 420, els. NASA Langley Research Center, Hampton, VA 23681. The present paper uses ERBS scanning radiometer E-mail: [email protected] broadband measurement data over a 5-yr period to com- 1529 Unauthenticated | Downloaded 10/03/21 12:51 AM UTC 1530 JOURNAL OF THE ATMOSPHERIC SCIENCES VOLUME 60 pute the diurnal cycle of OLR. A grid system of 2.58 variations of 50 W m22 over regions with deep con- regions covering the earth between 558N and 558Sis vective cycles. Extreme ranges of 100 W m22 (Atacama used. Diurnal cycles are de®ned for four 3 month sea- Desert in Peru) to 2 W m22 (some ocean regions) were sons, de®ned in section 3. This averaging process results found. In the mean they found the diurnal cycle of OLR in diurnal cycles being de®ned for over 6000 regions follows a half-sine variation, symmetric about noon. between 558N and 558S. To examine these in a system- This description was incorporated into data processing atic manner, the cycles are described in terms of prin- for ERBE when computing daily average values of cipal components, which use the data to de®ne the dom- OLR. Pinker et al. (1986), using GOES data for May± inant patterns. The time variations of the principal com- August 1982 noted a variety of patterns of diurnal cycle ponents and the geographical patterns of the correspond- of OLR and that a large sample is needed to develop ing empirical orthogonal functions provide a way to these models. describe and understand the cycles in terms of physical A dataset beginning June 1974 of nearly continuous processes which create them. data from seven National Oceanic and Atmospheric Ad- Since the paper by Raschke and Bandeen (1970), a minstration (NOAA) sun-synchronous satellites was de- number of articles have dealt with observational studies veloped by Gruber and Winston (1978) and Gruber and of the diurnal cycle of clouds and OLR, though some Krueger (1984). This valuable archive was subsequently were limited spatially, temporally, or in their use of used by Hartmann and Recker (1986), Gruber and Chen narrowband measurements. These are reviewed in the (1988), and Liebmann and Gruber (1988) to study the next section. diurnal cycles of clouds and radiation. Hartmann and Recker (1986) considered OLR for 308Nto308S. They determined the ITCZ and South Paci®c convergence 2. Background zone had similar ranges of 6 to 8 W m22 and a maximum This sections deals with the extensive literature avail- in the morning (0600±1200 LST) due to convective able concerning the study of the diurnal cycle of clouds clouds at ;400 mb. They also found diurnal variations and OLR. Due to the high temporal sampling rates of of very high clouds (;100 mb), 1808 out of phase with geosynchronous spacecraft many studies used data from variations at lower levels in atmosphere that reduced these satellites. This limited these studies to certain re- the magnitude of the diurnal harmonic. Results were gions of the globe and required conversion of narrow- presented as seasonal maps of the ®rst Fourier term of band radiances to broadband radiances, usually by cor- the diurnal cycle, using arrows to indicate magnitude relations. A Meteosat Second Generation (MSG-1), and phase for each region. Gruber and Chen (1988) spacecraft carrying the Geosynchronous Earth Radia- supplemented the same dataset with Nimbus-7 data to tion Budget (GERB) instrument, a broadband scanning expand the latitudinal range to 558Nto558S. Again radiometer, was launched in August 2002. using harmonic analysis, they showed large seasonal An early paper to study the diurnal cycle of OLR variations of the diurnal harmonic over midlatitude con- using geostationary data is Saunders and Hunt (1980). tinents. A seasonal difference of 5 W m22 at 1200 LST They considered four regions using Meteosat data and to ;16 W m22 at 1400 LST for January and July, re- found diurnal variations depended on scene type. Over spectively, was found. The maximum at local noon is ocean, high clouds, and low clouds, OLR remains fairly attributed to afternoon cloud growth. Liebmann and constant but over desert it varies during the day. They Gruber (1988) found a similar seasonal change in the estimated errors of diurnal mean OLR, based on mea- midlatitude diurnal cycle. With respect to the ITCZ they surements from a sun-synchronous spacecraft with 0900 found the maximum amplitude of the diurnal cycle, LST equator crossing, and computed a 9 W m22 error though small, migrated with the ITCZ along its seasonal for desert if the diurnal cycle is not considered when path. They point out that the semidiurnal harmonic com- calculating daily mean OLR. Schmetz and Liu (1988) ponent (not shown in their paper) often had a signi®cant also used Meteosat data to study the diurnal cycle of impact on areas of intense convection. four regions. By including the water vapor and 10.5± As ERBE data became available several studies fo- 12.5-mm window channels, they reduced the error of cused on information from this multisatellite radiation derived OLR by a factor of 2. The marine stratocumulus budget dataset. Harrison et al. (1988) showed ranges of region was found to have a diurnal cycle due to ab- OLR for all-sky and clear-sky conditions for April 1985 sorption of sunlight within the clouds, which dissipated using data from ERBE scanning radiometers aboard by midday allowing OLR to peak in the afternoon. For NOAA-9 and ERBS. Harrison et al. (1990) and Kon- the Sahara Desert they found a diurnal cycle that peaks dragunta et al.
Load more

Recommended publications
  • Indian Ocean Dipole and El Niño/Southern Oscillation Impacts on Regional Chlorophyll Anomalies in the Indian Ocean Jock C
    Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean Jock C. Currie, Matthieu Lengaigne, Jérôme Vialard, David M. Kaplan, Olivier Aumont, S. W. A. Naqvi, Olivier Maury To cite this version: Jock C. Currie, Matthieu Lengaigne, Jérôme Vialard, David M. Kaplan, Olivier Aumont, et al.. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean. Biogeosciences, European Geosciences Union, 2013, 10 (10), pp.6677 - 6698. 10.5194/bg-10-6677-2013. hal-01495273 HAL Id: hal-01495273 https://hal.archives-ouvertes.fr/hal-01495273 Submitted on 3 Aug 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Distributed under a Creative Commons Attribution - NoDerivatives| 4.0 International License Biogeosciences, 10, 6677–6698, 2013 Open Access www.biogeosciences.net/10/6677/2013/ doi:10.5194/bg-10-6677-2013 Biogeosciences © Author(s) 2013. CC Attribution 3.0 License. Indian Ocean Dipole and El Niño/Southern Oscillation impacts on regional chlorophyll anomalies in the Indian Ocean J. C. Currie1,2, M. Lengaigne3, J. Vialard3, D. M. Kaplan4, O. Aumont5, S. W. A.
    [Show full text]
  • Diurnal Cycle of Precipitation Amount and Frequency in Sweden: Observation Versus Model Simulation
    SERIES A DYNAMIC METEOROLOGY AND OCEANOGRAPHY PUBLISHED BY THE INTERNATIONAL METEOROLOGICAL INSTITUTE IN STOCKHOLM Tellus (2011), 63A, 664–674 C 2011 The Authors Tellus A C 2011 John Wiley & Sons A/S Printed in Singapore. All rights reserved TELLUS Diurnal cycle of precipitation amount and frequency in Sweden: observation versus model simulation ∗ By JEE-HOON JEONG1 ,ALEXANDER WALTHER1,GRIGORY NIKULIN2, DELIANG CHEN1,† and C O LIN JO N ES 2, 1Department of Earth Sciences, University of Gothenburg, Box 460, SE-405 30 Gothenburg, Sweden; 2Rossby Centre, SMHI, SE-601 76 Norrkoping,¨ Sweden (Manuscript received 31 July 2010; in final form 26 January 2011) ABSTRACT This study investigated the diurnal cycle of precipitation in Sweden using hourly ground observations for 1996–2008. General characteristics of phase and amplitude for the diurnal cycle of precipitation, both in amount and frequency, were identified. In the warm season (April–September), the ‘typical’ afternoon (14–16 LST) peaks are dominant over inland Sweden, whereas late night to early morning (04–06 LST) peaks with relatively weak amplitude are discernable in the east coast along the Baltic Sea. The diurnal variation is almost negligible in the cold season (October–March), due to the weak solar radiation at high latitudes. The variations of convective activity forced by solar heating and modulated by geographical characteristics were suggested as primarily factors to invoke the cycles and spatial variation identified. The observed cycle was compared with the cycle simulated by a regional climate model. The model fairly well captures the spatial pattern of the phase of the diurnal cycle. However, the warm season afternoon peak is simulated too early and too uniformly across the stations, associated with too frequent occurrences of convective rainfall events with relatively light intensity.
    [Show full text]
  • Understanding Diurnal Cycle Mode Intensification and Its Effect on Interannual and Interdecadal Warm Season Precipitation Trends Over the U.S
    Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2018 Understanding diurnal cycle mode intensification and its effect on interannual and interdecadal warm season precipitation trends over the U.S. Corn Belt Amanda Black Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Meteorology Commons Recommended Citation Black, Amanda, "Understanding diurnal cycle mode intensification and its effect on interannual and interdecadal warm season precipitation trends over the U.S. Corn Belt" (2018). Graduate Theses and Dissertations. 16791. https://lib.dr.iastate.edu/etd/16791 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Understanding diurnal cycle mode intensification and its effect on interannual and interdecadal warm season precipitation trends over the U.S. Corn Belt by Amanda Suzanne Black A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Meteorology Program of Study Committee: Xiaoqing Wu, Major Professor Tsing-Chang Chen Gene S. Takle Raymond W. Arritt William J. Gutowski The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred.
    [Show full text]
  • Moisture Origin As a Driver of Temporal Variabilities of The
    https://doi.org/10.5194/acp-2019-942 Preprint. Discussion started: 6 January 2020 c Author(s) 2020. CC BY 4.0 License. Moisture origin as a driver of temporal variabilities of the water vapour isotopic composition in the Lena River Delta, Siberia Jean-Louis Bonne1, Hanno Meyer2, Melanie Behrens1, Julia Boike2,3, Sepp Kipfstuhl1, Benjamin Rabe1, Toni Schmidt2, Lutz Schönicke2, Hans Christian Steen-Larsen4, Martin Werner1 5 1Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Bremerhaven, 27515 Germany 2Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung, Potsdam, 14401, Germany 3Geography Department, Humboldt-Universität zu Berlin, Berlin, 10099, Germany 4Geophysical Institute, University of Bergen, and Bjerknes Centre for Climate Research, Bergen, 5020, Norway Correspondence to: Jean-Louis Bonne ([email protected]), Martin Werner ([email protected]) 10 Abstract. In the context of the Arctic amplification of climate change affecting the regional atmospheric hydrological cycle, it is crucial to characterize the present-day’s moisture sources of the Arctic. The isotopic composition is an important tool to enhance our understanding of the drivers of the hydrological cycle, due to the different molecular characteristics of water stable isotopes during phase change. This study introduces two years of continuous in situ water vapour and precipitation isotopic observations conducted since July 2015 in the east-Siberian Lena delta, at the research station on the Samoylov 15 Island. The vapour isotopic signals are dominated by variations at the seasonal and synoptic time scales. Diurnal variations of the vapour isotopic signals are masked by synoptic variations, indicating low variations of the amplitude of local sources at the diurnal scale in winter, summer and autumn.
    [Show full text]
  • P1.6 Diurnal Cycles of the Surface Radiation Budget Data Set
    P1.6 DIURNAL CYCLES OF THE SURFACE RADIATION BUDGET DATA SET Pamela E. Mlynczak Science Applications International Corporation, Hampton, VA G. Louis Smith National Institute of Aerospace, Hampton, VA Paul W. Stackhouse, Jr. NASA Langley Research Center, Hampton, VA Shashi K. Gupta Analytical Services and Materials, Inc., Hampton, VA ABSTRACT weather and climate system. The annual cycle of radiation at the “top of the atmosphere” (TOA) has The Surface Radiation Budget Data Set been studied by Smith et al. (1990) and Bess et al. contains seven components describing radiation (1992), and the diurnal cycle of outgoing longwave flux: shortwave up, down and net, longwave up, radiation at TOA has been reported by Smith and down and net, and total radiation net. A principal Rutan (2003). Understanding the response of a component analysis has been used to study the dynamical system to a cyclical forcing is diurnal cycles of these components for an average fundamental to knowledge of the system’s July. The large thermal inertia of the ocean causes behavior. The nonlinear nature of the climate the diurnal cycle of its temperature to be quite system requires that we use information about the small, so the globe was partitioned into land and diurnal cycle to help to characterize the system. ocean for this study. For each of the seven One application of the results is to compare these components, one principal component describes results with the diurnal cycles that are computed more than 97% of the variance of the diurnal cycle by climate models. Another application is to for land except for downward longwave flux, for provide information for solar power studies.
    [Show full text]
  • C Copyright 2016 Stephen D. Po-Chedley on the Structure of Atmospheric Warming in Models and Observations: Implications for the Lapse Rate Feedback
    c Copyright 2016 Stephen D. Po-Chedley On the structure of atmospheric warming in models and observations: Implications for the lapse rate feedback Stephen D. Po-Chedley A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy University of Washington 2016 Reading Committee: Qiang Fu, Chair Kyle Armour Cecilia Bitz Program Authorized to Offer Degree: Department of Atmospheric Sciences University of Washington Abstract On the structure of atmospheric warming in models and observations: Implications for the lapse rate feedback Stephen D. Po-Chedley Chair of the Supervisory Committee: Professor Qiang Fu Department of Atmospheric Sciences This dissertation investigates the structure of atmospheric warming in observations and general circulation models (GCMs). Theory and GCMs suggest that warming is amplified in the tropical upper troposphere relative to the lower troposphere and the surface { a phenomenon known as vertical amplification. We assess model and observational agreement using several amplification metrics derived from the satellite-borne microwave sounding unit (MSU) atmospheric temperature trends. An important correction to the satellite microwave record is the removal of temperature drifts caused by changes in diurnal sampling. This correction the principal source of uncer- tainty in microwave temperature datasets. Furthermore, in three existing datasets, the ratio of tropical warming between the upper troposphere (T24 channel) and the surface (dT24/dTs ∼0.6 { 1.3) is lower than that of GCMs (∼1.4 { 1.6). To better understand these issues, we produced an alternate MSU dataset with an improved diurnal correction. We show that existing MSU datasets likely underestimate tropical mid-tropospheric temperature trends.
    [Show full text]
  • Downloaded 09/25/21 08:02 AM UTC
    3866 JOURNAL OF CLIMATE VOLUME 20 Investigation of the Summer Climate of the Contiguous United States and Mexico Using the Regional Atmospheric Modeling System (RAMS). Part II: Model Climate Variability CHRISTOPHER L. CASTRO* Department of Atmospheric Science, Colorado State University, Fort Collins, Colorado ROGER A. PIELKE SR. Cooperative Institute for Research in Environmental Sciences, Program in Atmospheric and Oceanic Sciences, University of Colorado, Boulder, Colorado JIMMY O. ADEGOKE Laboratory for Climate Analysis and Modeling, Department of Geosciences, University of Missouri—Kansas City, Kansas City, Missouri SIEGFRIED D. SCHUBERT AND PHILLIP J. PEGION NASA Goddard Laboratory for Atmospheres, Greenbelt, Maryland (Manuscript received 22 November 2005, in final form 27 November 2006) ABSTRACT Summer simulations over the contiguous United States and Mexico with the Regional Atmospheric Modeling System (RAMS) dynamically downscaling the NCEP–NCAR Reanalysis I for the period 1950– 2002 (described in Part I of the study) are evaluated with respect to the three dominant modes of global SST. Two of these modes are associated with the statistically significant, naturally occurring interannual and interdecadal variability in the Pacific. The remaining mode corresponds to the recent warming of tropical sea surface temperatures. Time-evolving teleconnections associated with Pacific SSTs delay or accelerate the evolution of the North American monsoon. At the period of maximum teleconnectivity in late June and early July, there is an opposite relationship between precipitation in the core monsoon region and the central United States. Use of a regional climate model (RCM) is essential to capture this variability because of its representation of the diurnal cycle of convective rainfall.
    [Show full text]
  • Cloud Radar Observations of Diurnal and Seasonal Cloudiness Over Reunion Island
    atmosphere Article Cloud Radar Observations of Diurnal and Seasonal Cloudiness over Reunion Island Jonathan Durand 1, Edouard Lees 1, Olivier Bousquet 1,2,*, Julien Delanoë 3 and François Bonnardot 4 1 Laboratoire de l’Atmosphère et des Cyclones (UMR8105 LACy), Université de La Réunion, CNRS, Météo-France, 97400 Saint-Denis, France; [email protected] (J.D.); [email protected] (E.L.) 2 Institute for Coastal Marine Research (CMR), Nelson Mandela University, Port-Elizabeth 6001, South Africa 3 Laboratoire Atmosphère, Milieux et Observations Spatiales (UMR 8190 LATMOS), CNRS/Sorbonne Université/USVQ, 78280 Guyancourt, France; [email protected] 4 Direction Interrégionale de Météo-France pour l’Océan Indien, Saint-Denis, 97490 Sainte-Clotilde, France; [email protected] * Correspondence: [email protected] Abstract: In November 2016, a 95 GHz cloud radar was permanently deployed in Reunion Island to investigate the vertical distribution of tropical clouds and monitor the temporal variability of cloudiness in the frame of the pan-European research infrastructure Aerosol, Clouds and Trace gases Research InfraStructure (ACTRIS). In the present study, reflectivity observations collected during the two first years of operation (2016–2018) of this vertically pointing cloud radar are relied upon to investigate the diurnal and seasonal cycle of cloudiness in the northern part of this island. During the wet season (December–March), cloudiness is particularly pronounced between 1–3 km above sea level (with a frequency of cloud occurrence of 45% between 12:00–19:00 LST) and 8–12 km (with Citation: Durand, J.; Lees, E.; a frequency of cloud occurrence of 15% between 14:00–19:00 LST).
    [Show full text]
  • Hidden Warming Effects of Cloud Cycle Errors in Climate Models Jun Yin1, Amilcare Porporato1,2*
    Hidden Warming Effects of Cloud Cycle Errors in Climate Models Jun Yin1, Amilcare Porporato1,2* Affiliations: 1Department of Civil and Environmental Engineering, Duke University, Durham, North Carolina, USA. 2Nicholas School of the Environment, Duke University, Durham, North Carolina, USA. *Correspondence to: [email protected] Abstract: Clouds’ efficiency at reflecting solar radiation and trapping the terrestrial one is strongly modulated by their diurnal cycle. Much attention has been paid to mean cloud properties due to their critical role in climate projections; however, less research has been devoted to their diurnal cycle. Here, we quantify the mean, amplitude, and phase of the cloud cycles in current climate models and compare them with satellite observations and reanalysis data. While the mean values appear to be reliable, the amplitude and phase of the diurnal cycles of clouds show marked inconsistencies, especially over land. We show that, to compensate for the increased net radiation input implied by such errors, an overestimation of the cloud liquid water path may be introduced during calibration of climate models to keep temperatures in line with observations. These discrepancies are likely to be related to cloud parametrization problems in relation to atmospheric convection. One Sentence Summary: Errors in diurnal cycle of clouds induce warming effects in climate models, likely compensated by the overestimation of cloud liquid water path. 1 Main Text: As efficient modulators of the Earth’s radiative budget, clouds play a crucial role in making our planet habitable (1). Their response to the increase in anthropogenic emissions of greenhouse gases will also have a substantial effect on future climates, although it is highly uncertain whether this will contribute to intensifying or alleviating the global warming threat (2).
    [Show full text]
  • Diurnal Characteristics of Precipitation Features Over the Tropical East Pacific: a Comparison of the EPIC and TEPPS Regions
    4068 JOURNAL OF CLIMATE VOLUME 21 Diurnal Characteristics of Precipitation Features over the Tropical East Pacific: A Comparison of the EPIC and TEPPS Regions R. CIFELLI Colorado State University, Fort Collins, Colorado S. W. NESBITT University of Illinois at Urbana–Champaign, Urbana, Illinois S. A. RUTLEDGE Colorado State University, Fort Collins, Colorado W. A. PETERSEN University of Alabama in Huntsville, Huntsville, Alabama S. YUTER North Carolina State University at Raleigh, Raleigh, North Carolina (Manuscript received 1 May 2007, in final form 1 November 2007) ABSTRACT This study examines the diurnal cycle of precipitation features in two regions of the tropical east Pacific where field campaigns [the East Pacific Investigation of Climate Processes in the Coupled Ocean– Atmosphere System (EPIC) and the Tropical Eastern Pacific Process Study (TEPPS)] were recently con- ducted. EPIC (10°N, 95°W) was undertaken in September 2001 and TEPPS (8°N, 125°W) was carried out in August 1997. Both studies employed C-band radar observations on board the NOAA ship Ronald H. Brown (RHB) and periodic upper-air sounding launches to observe conditions in the surrounding environ- ment. Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and Geostationary Opera- tional Environmental Satellite (GOES) IR data are used to place the RHB data in a climatological context and Tropical Atmosphere Ocean (TAO) buoy data are used to evaluate changes in boundary layer fluxes in context with the observed diurnal cycle of radar observations of precipitation features. Precipitation features are defined as contiguous regions of radar echo and are subdivided into mesoscale convective system (MCS) and sub-MCS categories.
    [Show full text]
  • Diurnal Cycles in Arctic Surface Radiative Fluxes in a Blended Satellite-Climate Reanalysis Data Set
    Journal of Applied Remote Sensing, Vol. 1, 013535 (13 September 2007) Diurnal cycles in Arctic surface radiative fluxes in a blended satellite-climate reanalysis data set Xuanji Wang*, Jeffrey R. Key†, Chuck Fowler+, James Maslanik& *Cooperative Institute for Meteorological Satellite Studies, University of Wisconsin-Madison Madison, Wisconsin 53706, USA [email protected] †Center for Satellite Applications and Research, NOAA/NESDIS, Madison, Wisconsin 53706, USA [email protected] +Colorado Center for Astrodynamics Research, University of Colorado, Boulder, Colorado, USA [email protected] & Cooperative Institute for Research in the Environmental Sciences, University of Colorado Boulder, Colorado, USA [email protected] Abstract. Surface radiative fluxes and their diurnal cycles are very important components in the surface energy budget of the Arctic, and also critical forcing variables for land surface models. An approach has been developed to derive diurnal cycles of the surface radiative fluxes for the Arctic from 6-hourly accumulated surface downward shortwave and longwave radiative fluxes in the European Center for Medium Range Weather Forecasts (ECMWF) 40- year reanalysis (ERA-40) products by “correcting” interpolated hourly values with twice- daily satellite-derived radiative fluxes. Ground-based measurements of the surface radiative fluxes at an Arctic meteorological station are used to validate the approach. Results show that the blended satellite-model products are in good agreement with the ground-based measurements. Based on this blended product, diurnal cycles of surface radiative fluxes are examined over time and space. It clearly shows that satellite-retrieved products in high spatial and temporal resolutions are more realistic and accurate, and can be used to adjust or “correct” the reanalysis products, especially for the polar region where there exist few ground based measurements for diurnal cycle studies.
    [Show full text]
  • The Consistency of MJO Teleconnection Patterns on Interannual Time Scales
    1MAY 2020 T S E N G E T A L . 3471 The Consistency of MJO Teleconnection Patterns on Interannual Time Scales KAI-CHIH TSENG,ERIC MALONEY, AND ELIZABETH A. BARNES Colorado State University, Fort Collins, Colorado (Manuscript received 10 July 2019, in final form 21 January 2020) ABSTRACT The Madden–Julian oscillation (MJO) excites strong variations in extratropical geopotential heights that modulate extratropical weather, making the MJO an important predictability source on subseasonal to seasonal time scales (S2S). Previous research demonstrates a strong similarity of teleconnection patterns across MJO events for certain MJO phases (i.e., pattern consistency) and increased model ensemble agreement during these phases that is beneficial for extended numerical weather forecasts. However, the MJO’s ability to modulate extratropical weather varies greatly on interannual time scales, which brings extra uncertainty in leveraging the MJO for S2S prediction. Few studies have investigated the mechanisms responsible for variations in the con- sistency of MJO tropical–extratropical teleconnections on interannual time scales. This study uses reanalysis data, ensemble simulations of a linear baroclinic model, and a Rossby wave ray tracing algorithm to demonstrate that two mechanisms largely determine the interannual variability of MJO teleconnection consistency. First, the meridional shift of stationary Rossby wave ray paths indicates increases (decreases) in the MJO’s extratropical modulation during La Niña(ElNiño) years. Second, a previous study proposed that the constructive interfer- ence of Rossby wave signals caused by a dipole Rossby wave source pattern across the subtropical jet during certain MJO phases produces a consistent MJO teleconnection. However, this dipole feature is less clear in both El Niño and La Niña years due to the extension and contraction of MJO convection, respectively, which would decrease the MJO’s influence in the extratropics.
    [Show full text]