feasibility of deriving surface and atmospheric parameters over land using trmm-tmi b. s. gohil,...

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