THE BENEFITS OF LIDAR FOR METEOROLOGICAL RESEARCH: THE CONVECTIVE AND OROGRAPHICALLY-INDUCED PRECIPITATION STUDY (COPS) Andreas Behrendt(1), Volker Wulfmeyer(1), Christoph Kottmeier(2), Ulrich Corsmeier(2) (1)Institute of Physics and Meteorology, University of Hohenheim, D-70593 Stuttgart, Germany, [email protected] (2) Institute for Meteorology and Climate Research (IMK), University of Karlsruhe/Forschungszentrum Karlsruhe, Karlsruhe, Germany ABSTRACT results of instrumental development within an intensive observations period. How can lidar serve to improve today's numerical Such a field experiment is the Convective and Oro- weather forecast? Which benefits does lidar offer com- graphically-induced Precipitation Study (COPS, pared with other techniques? Which measured parame- http://www.uni-hohenheim.de/spp-iop/) which takes ters, which resolution and accuracy, which platforms place in summer 2007 in a low-mountain range in and measurement strategies are needed? Using the next Southern-Western Germany and North-Eastern France. generation of high-resolution models, a refined model This area is characterized by high summer thunderstorm representation of atmospheric processes is currently in activity and particularly low skill of numerical weather development. Besides higher resolution, the refinements prediction models. COPS is part of the German Priority comprise improved parameterizations, new model phys- Program "Praecipitationis Quantitativae Predictio" ics – including, e.g., the effects of aerosols – and assimi- (PQP, http://www.meteo.uni-bonn.de/projekte/- lation of additional data. As example to discuss the role SPPMeteo/) and has been endorsed as World Weather lidar can play in this context we introduce the Convec- Research Program (WWRP) Research and Development tive and Orographically-induced Precipitation Study Project (Fig. 1). (COPS). The motivation of COPS is the fact that even It is the overarching objective of COPS to identify the with today's most advanced research models, the fore- physical and chemical processes responsible for the de- cast skills are especially low for convective precipita- ficiencies in quantitative precipitation forecast (QPF) tion in complex terrain. COPS will be conducted in over low-mountain regions and to improve their model Southern-Western Germany and North-Eastern France representation. Correspondingly, the overarching goal in summer 2007. During COPS a large suite of state-of- of COPS is to the-art remote sensing systems, ground-based and air- Advance the quality of forecasts of orographically- borne, partly scanning and employed for the first time, induced convective precipitation by 4D observations shall be combined with in-situ instruments. The meas- and modeling of its life cycle. urement strategies which involve state-of-the-art lidar An important tool to achieve this goal is the assimilation systems will be discussed and an outlook on the per- of additional data – especially from state-of-the-art lidar spectives of lidar in future meteorology will be given. systems. Data assimilation allows too separate models errors due to errors in the initial fields and errors in the 1. INTRODUCTION models' approximations of the relevant physical proc- esses (parameterizations). Furthermore, re-analyses test- Precipitation is the end product of a complex chain of ing the assimilation of different data, allow to investi- inter-coupled processes. As non-linear effects are in- gate the sensitivity of the models. volved, the correct forecast of precipitation depends COPS builds on a series of previous international meas- critically on both accurate initial fields and an adequate urement campaigns focusing on quantitative precipita- model representation of the relevant physical processes. tion forecast like the Mesoscale Alpine Program A comprehensive field experiment aimed at the im- (MAP), 1999, the International H2O Project provement of numerical weather prediction demands a (IHOP_2002), 2002, and the Convective Storm Initia- previously unachieved set of high-quality data that can- tion Project (CSIP), 2005. not be obtained by routine observations. In order to identify and distinguish between different kinds of 2. THE INITIATION OF CONVECTION model deficits and to improve initial conditions and process understanding, high-resolution data sets cover- Mesoscale studies in flat terrain during IHOP_2002 de- ing especially the entire evolution of convective precipi- monstrated the potential of high-resolution model runs tation events are needed. This can only be achieved by a for process studies [1, 2] and of ensemble forecasts for combination of sensors reflecting the most advanced sensitivity studies [3]. As characterization of the water vapor field was the key component of IHOP_2002, the ential absorption lidar (DIAL) of University of Hohen- performance of water vapor lidar systems was investi- heim (UHOH), Stuttgart, Germany, shall be applied. gated [4, 5] and the impact of high-resolution lidar ob- This instrument will be able to perform 2D water vapor servations for improving the prediction of convection measurements within one minute and will be collocated was highlighted by assimilation of airborne water vapor with the scanning rotational Raman lidar of UHOH [7]. DIAL measurements [6]. The synergy of these systems provides water vapor and In low-mountain regions, which cover the majority of temperature measurement from close to the ground up the Earth's land surface, the relevant processes leading to a range of several km. In the boundary layer, turbu- to convective precipitation are still hardly understood. lence and convection can be resolved. A scanning Dop- This is especially unsatisfactory as many severe weather pler lidar will be placed properly to get coincident water events are related to convective precipitation. vapor and wind measurements to calculate vertical tur- Open questions are related to the relative influence of bulent water vapor fluxes, and to localize the initiation the convergence and updrafts created by forced lift- and timing of convection onset. ing on the windward side and to thermally-forced The corresponding atmospheric fields expected at this anabatic flow, location during a pre-convective phase are shown in the wind shear profile in the region of the ridges, Fig. 3. variations in the depth of the convective boundary A scanning cloud radar will be operated at supersite 1 to layer as well as in moisture, convective inhibition monitor the transition from dry convection to cloud (CIN), and convective available potential energy formation and to get information on cloud particles. A (CAPE) across the mountain ridges, transect of micro-rain radars is used to measure the the presence of gravity waves impinging on the raindrop size distribution; one micro rain-radar is placed ridges, on the mountain top to obtain the initiation of precipita- aerosol load in the pre-convective environment in- tion and vertical profiles of rain rate. To derive the fluencing the diurnal cycle of boundary variables. mass, heat and moisture transport by thermally and ter- The latter topic demonstrates the importance of the in- rain driven wind regimes, sodars, as well as in situ tur- teraction between the initiation of convection and bulence stations are installed on the slopes. Energy bal- microphysical processes, i.e., the role of aerosols acting ance stations on top of the mountains and a setup of soil as cloud condensation nuclei. moisture sensors provide information on the importance Consequently, it is important to perform 4D thermody- of soil moisture, evapotranspiration and sensible heat namic measurements of atmospheric variables in the fluxes for the surface induced convection. troposphere in regions where initiation of convection is As part of the instrumental cluster of supersite 1, the expected as well as throughout its depth within and up- ARM mobile facility (AMF) will be operated during stream of the COPS region to assess its thermodynamic COPS in a valley. The AMF consists of a suite of in- (CAPE, CIN) and dynamic state (sharpness and pro- struments, among others, various radiometers for the gression of fronts, vorticity, moisture, and temperature detection of both infrared and microwave radiation, a advection). This requires a synergy of ground-based ceilometer, a micro-pulse lidar, a cloud radar, a precipi- scanning, airborne, and space borne remote sensing sys- tation radar, a radar wind profiler, and a radiosonde sta- tems. tion. For characterizing aerosols and for analyzing cloud microphysical properties at the cloud base, a multi- 3. THE ROLE OF LIDAR IN COPS AND SYSTEM wavelength Raman lidar, a scanning Doppler lidar, both SYNERGIES of the Institute for Tropospheric Research, Leipzig, Germany, and a scanning multi-channel microwave pro- Lidar systems are key components within COPS to in- filer will be added to the AMF. vestigate the initial clear-air fields of temperature, hu- Operation of Supersite 2 is planned for the lowlands of midity and wind before the initiation of convection and the Rhine valley. In contrast to Supersite 1, on top of the to detect and characterize aerosols. Hornisgrinde, the highest peak of the northern Black The ground-based instruments of COPS shall be con- Forest, this location is characteristic for rather flat sur- centrated in supersites in order to make optimum use of faces, the only landscape differences arising from land possible instrument synergies (Fig. 2). Each supersite use differences. Supersite 3 will be