Feasibility of Deriving Surface and Atmospheric Parameters over Land
using TRMM-TMI
B. S. Gohil, Atul K. Varma and A. K. MathurOceanic Sciences DivisionMeteorology and Oceanography GroupSpace Applications Centre (ISRO)Ahmedabad 380 015, India.
TB(,p) = TBDN ()(1-(TS, ,p)) +TS (TS, ,p) ()+TBUP
The brightness temperature received by microwave radiometer looking towards earth in non-scattering atmosphere in a thermodynamic equilibrium is given by:
TBDN
TBUP
SurfaceTs,
TB
TBS
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 50o incidence angle (Pedersen, 1988)
Assumption:
V19 V23 V37 = V
H19 H23 H37 = H
V or H 0
Constitution of database , TS, TBUP, TBDN, CLW, WV
• TS – 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
Parameter Min Max Mean SD
SST (K) 255 315 282.6 17.5
WV (g/cm2) 0.03 8.99 2.13 2.27
CLW (g/cm2) 0 0.19 0.05 0.05
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 CloudsCase: 1
Case: 2
Case: 3
Freezing level
Freezing level
Freezing level
CLW is maximum at freezing level
CLW (max) = 5% or 10% of cloud thickness in gm/m3
Raining clouds have not been considered
i2
BS
5
1iBM5
1ii
W*)T(TW
1
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 15 2002
IWV - July 16 2002
IWV - July 17 2002
IWV - June 1 2003
IWV - June 2 2003
Examples of Emissivity
Emissivity (V) -July 15 2002
Emissivity (V) - July 16 2002
Emissivity - July 17 2002
Emissivity - June 1 2003
Emissivity - June 2 2003
Examples of Emissivity Diff.(V-H)
Emissivity Difference (V-H) -July 15 2002
Emissivity Difference (V-H) -July 16 2002
Emissivity Difference (V-H) -July 17 2002
Emissivity Difference (V-H) -June 1 2003
Emissivity Difference (V-H) -June 2 2003
Examples of Land Surface Temperature (LST)
LST -July 15 2002
LST -July 16 2002
LST -July 17 2002
LST -June 1 2003
LST -June 2 2003
Examples of CLW
CLW - July 15 2002
CLW – July 16 2002
CLW - July 17 2002
CLW - June 1 2003
CLW - June 2 2003
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.
Thanks