Feasibility of Deriving Surface and Atmospheric Parameters over Land using TRMM-TMI B. S. Gohil, Atul K. Varma and A. K. Mathur Oceanic Sciences Division Meteorology and Oceanography Group Space Applications Centre (ISRO) Ahmedabad , India.
TB ( ,p) = TB DN ( )(1- (T S, ,p)) +T S (T S, ,p) ( )+TB UP The brightness temperature received by microwave radiometer looking towards earth in non-scattering atmosphere in a thermodynamic equilibrium is given by: TB DN TBUP Surface Ts, TB TB S For attenuation by atmospheric gases – Liebe (1992) model Absorption by non-precipitating clouds – Paris (1971)
Emissivities of (1) first year ice, (2) multiyear ice and (3) open water at H-polarization and 50 o incidence angle (Pedersen, 1988) Assumption: V19 V23 V37 = V H19 H23 H37 = H V or H 0
Constitution of database , T S, TB UP, TB DN, CLW, WV T S – from Climatology Pressure profiles simulated from hydrostatic equation V and H are proxy V is moved from 0.4 tp 1.0 and H such that H < V V-H = V - H = 0 to 0.6 ParameterMinMaxMeanSD SST (K) WV (g/cm 2 ) CLW (g/cm 2 )
Simulation of Water Vapor profiles RH is linearly varied from surface to tropopause RH is varied at the surface Temperature Lapse Rate of Standard Atmosphere are adopted WV profile is derived using RH and T profiles If clouds present RH = 100% at the base of the clouds Surface Tropopause (16 km) RH=0
Simulation of Clouds Case: 1 Case: 2 Case: 3 Freezing level CLW is maximum at freezing level CLW (max) = 5% or 10% of cloud thickness in gm/m 3 Raining clouds have not been considered
Minimization Wi is weight, that for water vapor taken as: 0.5 for 19 GHz 0.8 for 23 GHz 0.7 for 37 GHz
TMI Characteristics
Examples of IWV
IWV-July
IWV - July
IWV - July
IWV - June
IWV - June
Examples of Emissivity
Emissivity (V) -July
Emissivity (V) - July
Emissivity - July
Emissivity - June
Emissivity - June
Examples of Emissivity Diff. (V-H)
Emissivity Difference (V-H) -July
Emissivity Difference (V-H) -July
Emissivity Difference (V-H) -July
Emissivity Difference (V-H) -June
Emissivity Difference (V-H) -June
Examples of Land Surface Temperature (LST)
LST -July
LST -July
LST -July
LST -June
LST -June
Examples of CLW
CLW - July
CLW – July
CLW - July
CLW - June
CLW - June
TMI DERIVED GEOPHYSICAL PARAMETERS OVER LAND (JUN 3, ’03-15GMT) (Gohil, et al, 2003)Abs
Comparison NCEP Reanalysis Jun 03, 2003 (Daily Mean) TMI Derived WVC over Land (Jun 03, 2003/15 GMT)(Over ocean – Wentz Product)
Conclusion Study shows good prospects for estimation of Atmospheric and Surface parameters, especially water vapor over land. Study needs to be more refined with more case studies and inter-comparison/validation.
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