Intercomparison of deep convective cloud fractions from passive infrared and microwave radiance measurements

The common method to detect deep convective clouds is from satellite infrared (IR) measurements, which is based on thresholds of cloud-top temperatures. However, thick cirrus clouds with high cloud tops are difficult to screen out using IR methods, resulting in an overestimation of deep convective cloud fractions. Two aircraft cases with simultaneous Millimeter-wave Imaging Radiometer, Multispectral Atmospheric Mapping Sensor, and ER-2 Doppler radar measurements during the Convection and Moisture Experiment 3 in August 1998 are analyzed to investigate the influence of high thick cirrus clouds on two previously developed IR methods. In contrast, a microwave method based on the brightness temperature differences between the three water vapor channels around 183.3 GHz of the Advanced Microwave Sounding Unit-B (AMSU-B) (183.3/spl plusmn/1,183.3/spl plusmn/3, and 183.3/spl plusmn/7 GHz) can screen out high thick cirrus clouds efficiently. The tropical deep convective cloud fractions (30/spl deg/S-30/spl deg/N) estimated by the IR methods and the AMSU-B method are compared. Although their geographical distributions are in well agreement with each other, the total fractions detected by the IR methods are about 2-3.5 times greater than that detected by the AMSU-B method. Moreover, the overestimation of deep convective cloud fractions by the IR method (11-/spl mu/m brightness temperature less than 215 K) can result in a displacement in the detected location of the deep convective clouds. The average thick cirrus clouds cover 2.5 times the area of the deep convective clouds that generates them.

[1]  Brian E. Mapes,et al.  Multiscale variability of deep convection in relation to large-scale circulation in TOGA COARE , 1996 .

[2]  Toshiro Inoue,et al.  A cloud type classification with NOAA 7 split‐window measurements , 1987 .

[3]  A. Dessler.  The effect of deep, tropical convection on the tropical tropopause layer , 2002 .

[4]  Judith A. Curry,et al.  Classification of clouds over the western equatorial Pacific Ocean using combined infrared and microwave satellite data , 1995 .

[5]  J. Lelieveld,et al.  Role of Deep Cloud Convection in the Ozone Budget of the Troposphere , 1994, Science.

[6]  W. Rossow,et al.  Behavior of Deep Convective Clouds in the Tropical Pacific Deduced from ISCCP Radiances , 1990 .

[7]  J. Janowiak,et al.  The Global Precipitation Climatology Project (GPCP) combined precipitation dataset , 1997 .

[8]  Paul Racette,et al.  Storm-Associated Microwave Radiometric Signatures in the Frequency Range of 90 220 GHz , 1997 .

[9]  Ralf Bennartz,et al.  Sensitivity of microwave radiances at 85–183 GHz to precipitating ice particles , 2003 .

[10]  A. Slingo,et al.  Simulation of the diurnal cycle in a climate model and its evaluation using data from Meteosat 7 , 2004 .

[11]  Albin J. Gasiewski,et al.  Influence of microphysical cloud parameterizations on microwave brightness temperatures , 2002, IEEE Trans. Geosci. Remote. Sens..

[12]  B. Soden,et al.  Diurnal cycle of convection, clouds, and water vapor in the tropical upper troposphere: Satellites versus a general circulation model , 2004 .

[13]  W. M. Gray,et al.  Diurnal Variation of Deep Cumulus Convection , 1977 .

[14]  T. Inoue.  Deep convection observed from split window of GOES and PR/TRMM, LIS/TRMM , 2003, IGARSS 2003. 2003 IEEE International Geoscience and Remote Sensing Symposium. Proceedings (IEEE Cat. No.03CH37477).

[15]  H. Laurent,et al.  Diurnal march of the convection observed during TRMM‐WETAMC/LBA , 2002 .

[16]  R. Hemler,et al.  A study of the impact of the Intertropical Convergence Zone on aerosols during INDOEX , 2002 .

[17]  K. Lau,et al.  Diurnal Variations in Tropical Oceanic Cumulus Convection during TOGA COARE , 1997 .

[18]  William S. Olson,et al.  Structure of Florida Thunderstorms Using High-Altitude Aircraft Radiometer and Radar Observations , 1996 .

[19]  J. Comstock,et al.  Evaluation of tropical cirrus cloud properties derived from ECMWF model output and ground based measurements over Nauru Island , 2004 .

[20]  T. Hall,et al.  The Diurnal Cycle of West Pacific Deep Convection and Its Relation to the Spatial and Temporal Variation of Tropical MCSs , 1999 .

[21]  A. Gettelman,et al.  Distribution and influence of convection in the tropical tropopause region , 2002 .

[22]  H. Hendon,et al.  The diurnal cycle of tropical convection , 1993 .

[23]  David H. Staelin,et al.  AIRS/AMSU/HSB precipitation estimates , 2003, IEEE Trans. Geosci. Remote. Sens..

[24]  Jungang Miao,et al.  Detection of tropical deep convective clouds from AMSU-B water vapor channels measurements , 2005 .

[25]  Patrick Minnis,et al.  Underestimation of deep convective cloud tops by thermal imagery , 2004 .

[26]  C P Rinsland,et al.  Enhanced Upper Tropical Tropospheric COS: Impact on the Stratospheric Aerosol Layer , 2003, Science.

[27]  Andrew E. Dessler,et al.  Observations of deep convection in the tropics using the Tropical Rainfall Measuring Mission (TRMM) precipitation radar , 2002 .

[28]  Cirrus detrainment‐temperature feedback , 1999 .

[29]  Dong L. Wu,et al.  Geographical distribution and interseasonal variability of tropical deep convection: UARS MLS observations and analyses , 2004 .

[30]  J. Holton,et al.  Stratosphere‐troposphere exchange , 1995 .

[31]  Xiangqian Wu,et al.  Effects of precipitation and cloud ice on brightness temperatures in AMSU moisture channels , 1997, IEEE Trans. Geosci. Remote. Sens..