ORIGINAL PAPER Impact of assimilation of ATOVS temperature and humidity and SSM/I total precipitable water on the simulation of a monsoon depression M. Govindankutty • A. Chandrasekar Received: 5 May 2010 / Accepted: 14 May 2011 Ó Springer Science+Business Media B.V. 2011 Abstract The present study explored the effect of assimilation of Advanced TIROS Vertical Sounder (ATOVS) temperature and humidity profiles and Spectral sensor microwave imager (SSM/I) total precipitable water (TPW) on the simulation of a monsoon depression which formed over the Arabian Sea during September 2005 using the Weather Research and Forecast model. The three-dimensional variational (3DVAR) data assimi- lation technique has been employed for the purpose of assimilation of satellite observa- tions. Statistical scores like ‘‘equitable threat score,’’ ‘‘bias score,’’ ‘‘forecast impact,’’ and ‘‘improvement parameter’’ have been used to examine the impact of the above-mentioned satellite observations on the numerical simulation of a monsoon depression. The diag- nostics of this study include verification of the vertical structure of depression, in terms of temperature anomaly profiles and relative vorticity profiles with observations/analysis. Additional diagnostics of the study include the analysis of the heat budget and moisture budget. Such budget studies have been performed to provide information on the role of cumulus convection associated with the depression. The results of this study show direct and good evidence of the impact of the assimilation of the satellite observations using 3DVAR on the dynamical and thermodynamical features of a monsoon depression along with the effect of inclusion of satellite observation on the spatial pattern of the simulated precipitation associated with the depression. The ‘‘forecast impact’’ parameter calculated for the wind speed provides good evidence of the positive impact of the assimilation of ATOVS temperature and humidity profiles and SSM/I TPW on the model simulation, with the assimilation of the ATOVS profiles showing better impact in terms of a more positive value of the ‘‘forecast impact’’ parameter. The results of the study also indicate the M. Govindankutty Department of Physics and Meteorology, Indian Institute of Technology, Kharagpur, India A. Chandrasekar (&) Department of Earth and Space Sciences, Indian Institute of Space Science and Technology, Thiruvananthapuram, India e-mail: chandra@iist.ac.in 123 Nat Hazards DOI 10.1007/s11069-011-9857-x