Investigation of Atmospheric Boundary Layer

NEW TECHNOLOGY FOR INVESTIGATION OF URBAN AREA ATMOSPHERIC BOUNDARY LAYER

Kadygrov E.N.1, Kuznetsova I.N.2, Ivanov A.A.1, Liakhov A.A.3

1 - Central Aerological Observatory, Roshydromet, 3 - Pervomayskaya Str., Dolgoprudny, Moscow Reg., 141700, Russia, Tel. (+7)(095) 579-9455, Fax.: (+7)(095) 408-7758, e-mail: [email protected]

2 - Hydrometeorological Center, Roshydromet, Moscow, Russia

3 – Moscow Weather Forecast Bureau, Moscow, Russia

1. Introduction

Near-surface data from meteorological stations at the city and in suburb were often used for investigation of heat island above urban area (Kondratiev and Matveev, 1999). New technology based on consuming of microwave temperature profilers gave possibility to provide more detail investigation of heat island parameters. During 2000-2002 three microwave temperature profilers (MTP-5) were used simultaneously in Moscow region for continuous measurements of atmospheric boundary layer (ABL) temperature profile. One MTP-5 was installed in the center of Moscow city, the second – in the north part of Moscow (Dolgoprudny), and the third – in about 50 km westward from the Moscow city center (Zvenigorod experimental site of the Russian Academy of Science). The MTP-5 instrument is an angular-scanning single channel microwave radiometer that can provide temperature profile measurements each 10 minutes within the altitude range 0600 m with an accuracy 0,50C (Kadygrov and Pick, 1998; Kadygrov et al 1998; Westwater et al 1999).

It were three main scientific objectives for the simultaneous measurements. The first one was determination of a Megacity impact to the ABL parameters, which led to creation of heat island (Kondratiev K.Y. and Matveev L.T., 1999; Golitsin et al, 2002). The second objective was investigation of the ABL stability and its influence on a radiation balance near the ground surface. For that reason the collection of continuous data about ABL temperature profiles in different synoptical situations was provided. And the third objective was in the comparison of simultaneous ABL temperature profiles in Zvenigorod and Dolgoprudny where radiosonde data was obtained. It is necessary to underline that all preceding climatological data set about temperature inversion in whole Moscow Region was collected on the base of radiosonde data obtained in Dolgoprudny. That's why the comparison of ABL temperature profiles in two points separated by space on tenth of kilometers seems to be very interesting. The measurements were provided as a part of WMO pilot project GURME – Global Urban Meteorology and Environment (WMO Report, 1999).

2. Analysis of simultaneous remote sensing data

The data received by the use of simultaneous remote sensing of ABL temperature profiles has shown essential differences of thermal regime in the center of a big city and in suburb. In general: the annual average ABL condition in the central part of Moscow is close to unstable (adverse conditions), and deterioration of the vertical exchange conditions has a brief disposition. The monthly averaged temperature gradients in Moscow city center are presented in Table 1 and Table 2 as a function of a local time (on the base of MTP-5 data).

The data shows that the atmosphere has unstable temperature stratification during the night and early on the morning and not only in layer 0-100 m (Table 1) but also in the layer 0300 m (Table 2). Thermal turbulence has a minimum between 3 and 6 o’clock on the morning. On the base of MTP-5 data, it was experimentally confirmed that influence of a big city microclimate is comparable with influence of a large-scale meteorological processes during a number of synoptic situations. Within such events the heating from anthropogenic sources dominates radiation cooling of the lowest atmospheric layer. Table 1 Table 2 Monthly averaged temperature gradients (0C/100 m) Monthly averaged temperature gradients (0C/100 m) in the in the layer 0-100 m in the center of Moscow city layer 0-300 m in the center of Moscow city

Time July July Time July July October April January October April January (h) 2000 2001 (h) 2000 2001 0 -0,48 -0,53 -0,51 -0,54 -0,70 0 -0,54 -0,55 -0,75 -0,57 -0,67

3 -0,35 -0,30 -0,54 -0,42 -0,35 3 -0,41 -0,31 -0,77 -0,49 -0,29

6 -0,25 -0,15 -0,56 -0,30 -0,13 6 -0,34 -0,22 -0,78 -0,44 -0,12

9 -0,27 -0,47 -0,58 -0,68 -0,97 9 -0,43 -0,75 -0,81 -0,88 -1,24

12 -0,76 -1,16 -0,70 -0,91 -1,38 12 -0,99 -1,44 -0,97 -1,09 -1,67

15 -0,93 -1,37 -0,80 -1,12 -1,52 15 -1,10 -1,71 -1,04 -1,37 -1,90

18 -0,80 -1,24 -0,71 -1,04 -1,22 18 -0,87 -1,50 -0,92 -1,29 -1,55

21 -0,60 -0,86 -0,73 -0,89 -1,07 21 -0,59 -0,87 -0,95 -1,02 -1,24 Table 4 Recurrence of temperature inversion (%) in Moscow city center

Table 3 Month I II III IV V VI VII VIII IX X XI XII  CLIMATE Temperature ( C) at the layer 0-600 m on the base 49 43 36 35 36 34 35 38 38 33 41 42 of MTP-5 data in Moscow city center (M), in (RADIOSONDE) MTP-5 10 (2000г) Dolgoprudny (D), and in Zvenigorod (Z). March 2000-2001 32 18 35 57 32 23 35 29 27 35 20 3 31, 2001 (2001г) Fig. 1. Temperature fields in Dolgoprudny, Moscow and Zvenigorod (23 July 2001). n e o m m m m m m i

t m m 0 0 0 0 0 0 i a 0 0 0 0 0 0 0 t T 1 2 3 4 5 6 S

M 0:00 -1,6 -2,2 -2,9 -3,4 -3,9 -4,4 -5

D 0:00:00 -4,9 -4,6 -4,3 -4,3 -4,5 -4,6 -4,5 Z 0:00 -5,5 -4,5 -4,3 -4,3 -4,3 -4,5 -4,9 M 3:00 -4 -4,2 -4,1 -4,1 -4,2 -4,5 -4,7 D 3:00:00 -6,3 -5,4 -4,7 -4,5 -4,4 -4,4 -4,3 Z 3:00 -8,3 -5,5 -3,9 -3,1 -2,7 -2,9 -2,8 M 6:20 -6,2 -5,8 -4,8 -4,2 -3,7 -3,5 -3,6 D 6:00:00 -7,5 -6 -4,9 -4,4 -4,4 -4,4 -4,4 Z 6:00 -11 -7,6 -5,1 -3,7 -3 -2,6 -2,1 M 9:00 -4,8 -4,8 -4,3 -3,7 -3,4 -3,4 -3,6 D 9:00:00 -5,3 -4,8 -4,2 -4,2 -4,3 -4,5 -4,5 Z 9:00 -7,5 -6,2 -4,8 -3,9 -3,6 -3,4 -3,3 M 12:00 1,9 0,4 -0,9 -2 -2,8 -3,5 -4 D 12:00:00 0,8 -0,4 -1,1 -1,8 -2,5 -2,9 -3,4 Z 12:00 1 -0,4 -1,7 -2,7 -3,6 -4,4 -5,1 M 15:00 5,4 3,7 2,6 1,7 0,7 -0,3 -0,9 D 16:30:00 Z 15:00 4,1 2,6 1,1 -0,3 -1,4 -2,3 -3,2 M 18:00 7,5 5,7 4,4 3,4 2,3 1,4 0,5 D 18:00:00 5,2 4,2 3,5 2,7 2,1 1,5 0,9 Z 18:00 4,9 3,9 2,6 1,4 0,1 -0,9 -1,8 M 21:00 5,4 5 4,4 3,7 2,9 2,3 1,5 D 21:00:00 2,8 2,9 2,8 2,4 1,9 1,5 1,1 Z 21:01 -0,1 1,6 2,1 2,3 2,2 1,7 1,3 Three-points simultaneous remote sensing observations firstly gave detail quantitative parameters of temperature inversion, ABL stability and it’s differences in the center of urban area and in outside (Table 3). On the base of MTP-5 data for central part of Moscow were calculated the recurrence of temperature inversion (Table 4) and were compared with previous radiosonde data (Klinov, 1995).

Remote sensing data has sufficient differences with radiosonde data, particularly during wintertime – from November up to February. The recurrence of inversion for that time was less for 17-39% with respect to climatological data. In contrast, the April recurrence was 20% more than climatological data. As it was mentioned above, climatological data for Moscow city center were calculated on the base of radiosonde data from Dolgoprudny upper-air station (WMO index 27612). Therefore, the first reason for inversion recurrence differences may be in urban heat island influence (big difference between surface-atmosphere exchange in the center and in the north part of Moscow). And the second reason is that those radiosondes are normally released at 02.30 a.m. local time. But most of temperature inversions in April are started after those time and that is why were not detected by the radiosonde data.

During simultaneous remote sensing measurements were indicated differences in thermal regime of ABL in Moscow, in Dolgoprudny and in Zvenigorod station. On the Fig. 1 are presented temperature fields in Moscow city center, in Dolgoprudny and in Zvenigorod for anticyclone environment (23 July 2001). Fig. 2 presents the parameters of temperature inversions for the same places and within the same time.

Fig. 2. Parameters of temperature inversion in Moscow, Dolgoprudny and Zvenigorod (23-24 July 2001)

The temperature inversions were indicated in all three points of observations on the night. The deepest one was about 60C in Zvenigorod, 3.50C – in Dolgoprudny and 1.01.50C – in Moscow, and the inversion height was 470 m, 370 m and 300 m relatively. Dissipation of inversion is started firstly in Moscow, than in Dolgoprudny, and than in Zvenigorod.

The quantitative parameters of Moscow heat island are a dark spot in city climate understanding. Heat island parameters and its seasonal and daily variations were learned during anticyclone conditions. It was classified two main type of heat island. The specific parameters of the 1-st type were: – heat dome top has an altitude up to 600 m; - ABL temperature in the city is higher than in suburb. This type of heat island was indicated mostly in cold season, or in all seasons with high cloud density, or in warm seasons during cloudless night.

The specific parameters of the second type of heat island were: – heat dome top has an altitude up to 300 m; - above this altitude the temperature in suburb is higher than in the city center. This type of heat island is formed mostly by convective processes. One of an explanation for that type of head island could be done as the next: The bottom part of ABL in the city has faster heating because of turbulence exchange. The top part of ABL has faster cooling due to mixing with cold air from highest altitudes. The influence of city heat island to the suburb ABL is very dependent on wind speed and wind directions. It was observed that ABL thermal regime in Dolgoprudny looks like more close to Moscow city center than to Zvenigorod. On the Fig. 3 are presented some typical results of remote sensing temperature profile received in Dolgoprudny and in Zvenigorod in comparison with the radiosonde data obtained in Dolgoprudny.

24.06.2001 3:40am MTP-5 600 Dolgoprudny MTP-5 500 Zv enigorod Radiosonde 400 Dolgoprudny ] m [

t 300 h g i e H

12 13 14 15 16 17 18

Te mpe ra t u re [ C o ]

Fig. 3. Comparison of ABL temperature profiles In Dolgoprudny and in Zvenigorod (24 June 2001)

3. Conclusions

The results of simultaneous remote sensing measurements of ABL temperature profiles can be summarized as follows: - first time it was obtained quantitative parameters of heat island in ABL of Moscow Megacity for different seasons and miscellaneous of synoptic conditions; - proposed new technology can be very useful for urban research meteorology and environment - it was detected that radiosonde data obtained in Dolgoprudny are not fully representative for determination of ABL parameters on Zvenigorod experimental site because of Moscow Megacity heat island influence.

4. Acknowledgments

This study was partially supported by the Russian Science Foundation (RFFR grant N 01-05-64138).

5. References

Kadygrov E.N., and D.R. Pick, 1998. The potential for temperature retrieval from an angular-scanning single- channel microwave radiometer and some comparisons with in situ observations. Meteorological Application, vol. 5, pp. 393-404

Westwater E.R., Han Y., Irisov V.G., Leuskiy V., Kadygrov E.N., and Viazankin S.A., 1999. Remote sensing of boundary layer temperature profiles by a scanning5-mm microwave radiometer and RASS: comparison experiments. Journal of Atmospheric and Ocean Technology, vol. 16, N 7, pp. 805-818

Kadygrov E.N., Gaikovich K.P., Westwater E., Han Y., and Widener K., 1998. Potential performance of boundary layer temperature profile microwave remote sensing: results of field testing at various latitude zones. Proc. of the Eighth ARM Science Team Meeting. March 23-27, Tucson, Arizona, pp. 353-356

Kondratiev K.Y., and Matveev L.T., 1999. Main factors in forming of big city heat island. Reports of Russian Academy of Science, vol. 367, N 2, pp. 253-256 (in Russian)

Golitsin G.S., Kadygrov E.N., Kuznetsova I.N., 2002. Investigations of heat island on the base of microwave remote sensing data. Reports of Russian Academy of Science, vol. 385, N4, pp 1-8 (In Russian)

Klinov F.Y. (Editor), 1995. Climate, weather and ecology of Moscow. Hydrometeoizdat, Saint-Petersburg, Russia, p. 437 (in Russian)