D. Trochkine, V. Pavlov, I. Sutorikhin, A. Romanov, N. Bezuglova, G. Zinchenko

Transcription

1 Seasonal change of water content in the atmosphere over the West Siberia on the basis of remote sensing using ENVISAT (ESA) D. Trochkine, V. Pavlov, I. Sutorikhin, A. Romanov, N. Bezuglova, G. Zinchenko Institute for water and environmental problem SB RAS Russia, , Barnaul, Molodezhnaya st., 1, This work was supported by European Space Agency (ESA) provided access to MERIS (ENVISAT) data under the grant #4747.

2 ENVISAT 2

3 Instruments onboard ENVISAT 3

4 MERIS overview The Medium Resolution Imaging Spectrometer (MERIS) instrument produces multispectral images (in 15 selected spectral bands between 390 nm and 1040 nm) obtained in a downward viewing pushbroom imaging gmanner. The 15 bands acquire radiance in the visible and near infra-red bands. MERIS measurement data are used to derive information including: ocean color parameters in open waters such as chlorophyll and coastal waters parameters such as chlorophyll, dissolved organic matter, and suspended solid matter concentrations, characteristics of clouds, such as top pressure and optical thickness, the presence of vegetation and derived indices to characterize vegetation vigor, and atmosphere parameters such as aerosol optical thickness, aerosol type, and water vapor column contents. 4

5 MERIS Instrument Characteristics (wavelengths) Centre (nm) Bandwidth (nm) Use Yellow substance and detrital pigments Chlorophyll absorption maximum Chlorophyll and other pigments Suspended sediment, red tides Chlorophyll absorption minimum Suspended sediment Chlorophyll absorption and fluo. reference Chlorophyll fluorescence peak Fluo. reference, atmospheric corrections Vegetation, cloud O 2 R-branch absorption band Atmosphere corrections Vegetation, water vapour reference Atmosphere corrections Water vapour, land 5

6 Geolocation and connections with meteo parameters Clouds and water vapor set (Low resolution) Geolocation 6

7 Basis for studying of clouds water content For studying water content of clouds we analyzed distribution of cloud optical thickness on the number of pixels with clouds. Water content LWP depends on optical thickness of clouds directly by equation τ=3lwp/2ρr ef, where ρ - water density, and r ef -effective radii of cloud droplets. For the LWP estimations common value of = 13 μm were used (revised value 12 μm). Preliminary type of the distribution function over the West Siberia (limited by E longitude, and N latitude) were established. 7

8 Example of LWP over West Siberia on August 10, 2008 Latitude Салехард Ханты-Мансийск Александровское > Омск Томск Новосибирск Барнаул Longitude 8

9 Data selection 9

10 Study of spatial characteristics

11 Example of selection of area with different distribution ib i of Clouds Optical Thickness

12 Distribution of Cloud Optical Thickness logarithm on the number of pixels with clouds 0.50 N x4_point_24 Total 4x4_point_5 4x4_point_ Lg(τ)

13 Comparison of 4 x4 area distribution with 4 included 2 x2 distributions 0.40 N x Lg(τ)

14 0.50 N Comparison of 4 x4 area distribution with 16 included 1 x1 distributions x Lg(τ)

15 Study of temporal characteristics 1 N Portion of Cloud-free pixels _04_ _04_17 15

16 Monthly averaged portion of cloud- free pixels over West Siberia N

17 Distribution of Water Vapor Content logarithm on the number of pixels without ih clouds 0.7 april N may 0.6 june july august september January Jl July october november december january february march april may june 0 Lg(W)

18 Variation of water vapor content (W, g/m 2 ) over the West Siberia 2.5 Averaged lg(w) Averaged Lg(W) Averaged W Averaged Water vapour content W(g/m 2 ) Month

19 Distribution of Cloud Optical Thickness logarithm on the number of pixels with clouds 0.25 april may N june july august september 0.2 october november december january february march april may 0.15 june Lg(τ)

20 Variation of Cloud Optical Thickness (τ) over the West Siberia 80 τ Averaged τ Averaged Lg(τ) Lg(τ)

21 Reproducibility of Clouds Optical Thickness Distribution June 08 June May 08 May 09 May 09(14 31)

22 Seasonal change of water content in the atmosphere over the West Siberia g/m av LWP av W Total Total content is considering portions of Cloud and Cloud-free Pixels!!! 22