Classification of clouds over the western equatorial Pacific Ocean using combined infrared and microwave satellite data

Abstract

A new cloud classification scheme is presented that combines infrared and microwave satellite data. Because microwave radiation can penetrate deep into the cloud layer, this scheme is able to determine characteristics for both thin and deep clouds. Additionally, the new scheme can provide information on precipitation, which traditional infrared‐visible cloud classification schemes have been unable to. The proposed cloud classification scheme utilizes the cloud top temperature obtained from infrared measurements and a microwave index that includes both emission and scattering signals. The following eight cloud classes are defined: warm nonprecipitating cloud, warm precipitating cloud, midtop nonprecipitating cloud, midtop precipitating cloud, thin high‐top nonprecipitating cloud, deep high‐top nonprecipitating cloud, anvil with stratiform precipitating cloud, and deep convective precipitating cloud. The classification scheme is validated by aircraft radar data obtained from Tropical Ocean‐Global Atmosphere Coupled Ocean‐Atmosphere Response Experiment. The new cloud classification scheme is used to investigate the clouds in the western equatorial Pacific Ocean warm pool region for the period from November 1992 to February 1993, allowing us to obtain for the first time the spectra of cloud coverage and precipitation distribution as a function of cloud types. The analysis shows that most of the cloudiness in this region is associated with warm nonprecipitating clouds. Precipitating pixels comprise only about 15% of total cloud pixels. Of the precipitating pixels, about 50% have cloud top temperatures warmer than −40°C. Using rainfall rates obtained from microwave satellite data, the relative contribution by each precipitating cloud type is investigated. It is found that the precipitating clouds with cloud top temperature warmer than −40°C contribute at least 23% of the total rainfall amount, while the remaining 77% of total precipitation is divided almost equally by anvil with stratiform precipitating cloud and the deep convective precipitating cloud.

A Cloud and Precipitation Feature Database from Nine Years of TRMM Observations

“…There were studies of clouds conducted by grouping pixels with infrared brightness temperatures colder than certain criteria (e.g., Mapes and Houze 1992;Liu et al 1995;Chen et al 1996) and studies of precipitation systems by grouping pixels with cold microwave brightness temperature (e.g., Mohr and Zipser 1996;Toracinta and Zipser 2001) or by grouping pixels with valid precipitation radar echoes (e.g., Geerts 1998;Cifelli et al 2007). However, when several satellite instruments target the same object, different instruments and their measurands have their own characteristics and give different perspectives.…”

Introducing multisensor satellite radiance-based evaluation for regional Earth System modeling

“…The previous sections show the Tb 11μm sensitivity to the T CT and microwave Tb sensitivity to ice aloft. If these are combined, it allows a more complete view of cloud-precipitation processes [Liu et al, 1995]. Figures 7a and 7b shows the MODIS Tb 11μm (below 273 K, gray shade) overlaid with the AMSR-E Tb 89GHz(V) (below 270 K, color shade).…”

Extension of a Multisensor Satellite Radiance-Based Evaluation for Cloud System Resolving Models

“…We compare the results of the spherical assumption with those of the nonspherical databases in the Liu simulator (Liu 2008;Nowell et al 2013). Liu et al (1995) presented a cloud classification method using the CTT of a geostationary meteorological satellite (GMS)-4 and a microwave index from the scattering and emission channels of the special sensor microwave/imager (SSM/I) over ocean. Matsui et al (2014) introduced an evaluation method based on joint diagrams using the CTT (MODIS 11-μm TBs) and the PCT89 of AMSR-E to classify cloud types over land, following Liu et al (1995).…”

“…Liu et al (1995) presented a cloud classification method using the CTT of a geostationary meteorological satellite (GMS)-4 and a microwave index from the scattering and emission channels of the special sensor microwave/imager (SSM/I) over ocean. Matsui et al (2014) introduced an evaluation method based on joint diagrams using the CTT (MODIS 11-μm TBs) and the PCT89 of AMSR-E to classify cloud types over land, following Liu et al (1995). The two previous studies used the microwave index and PCT89 to distinguish between non-precipitation and precipitation clouds.…”