Over-Ocean Validation of the Global Convective Diagnostic

Abstract

The global convective diagnostic (GCD) is a bispectral (infrared and water vapor), day-night scheme for operationally mapping deep convection by means of geostationary satellite images. This article describes a test of GCD performance over tropical and subtropical waters near North America. The test consists of six cases, each involving a convective cloud complex. A seventh case treats convection over land. For each case, a map of deep convection was constructed from image pairs from Geostationary Operational Environmental Satellite-12 (GOES-12). Case by case and for all maritime cases together, the GCD map was compared with a convective parameter derived from the radar on the Tropical Rainfall Measuring Mission (TRMM), a polar-orbiting satellite. In general, each GCD map showed a bloblike feature. In each case, the radar convective pixels typically fell within the GCD blob. However, (except for the land case) the GCD predicted far too many convective pixels. In the maritime cases overprediction was reduced (without correspondingly impairing other measures of performance) by lowering the nominal GCD threshold. With this adjustment in place, for the six maritime cases taken individually, the GCD tended to yield more consistent results than did a monospectral (infrared) convective scheme. With the cases combined, at the lower threshold the GCD performed somewhat better than one of the more stable versions of the infrared scheme. Comparison with lightning events (also observed by TRMM) suggests the possibility of future improvement to the GCD through the incorporation of geostationary satellite observations of lightning.

A Prototype Method for Diagnosing High Ice Water Content Probability Using Satellite Imager Data

“…Tech. Discuss., https://doi.org/10.5194/amt-2017- deep convective anvil detection is the brightness temperature difference (BTD) between the ~6.5 µm water vapor (WV) and ~10.7 µm window (BTW) channels (Schmetz et al, 1997;Martin et al, 2008). Comparisons of the BTD product with CloudSat Cloud Profiling Radar observations indicate that positive BTD values are effective for detection of deep convection, often with a cloud vertical thickness exceeding 12 km (Young et al, 2012).…”

Combined MW-IR Precipitation Evolving Technique (PET) of convective rain fields

“…GCD is a method for recognizing deep convection from geostationary satellite images, both day and night, based on the difference from thermal infrared and water vapor channels. By using Precipitation Radar (PR) onboard the Tropical Rainfall Measurement Mission (TRMM), Martin et al (2008) noted that GCD generally produces more accurate deep-convection observation than any other monospectral infrared convective scheme.…”

PM-GCD – a combined IR–MW satellite technique for frequent retrieval of heavy precipitation

“…GCD is a bispectral day and night scheme (based on thermal infrared and water vapor channels) for deep convection operational mapping of geostationary satellite images. Referring to deep-convection observations from the Precipitation Radar (PR) onboard the Tropical Rainfall Measurement Mission (TRMM), Martin et al (2008) noted that GCD produces more accurate results than any monospectral infrared convective scheme.…”

“…However, these observations are taken from low-Earth-orbit (LEO) satellites and therefore do not provide satisfactory coverage of rapidly evolving precipitation systems. To solve this problem, over the past two decades several techniques have been developed that combine accurate MW-based rain rate estimates with frequent infrared (IR) observations from geosynchronous (GEO) satellites (Adler et al, 1993;Xu et al, 1999;Bellerby et al, 2000;Sorooshian et al, 2000;Turk et al, 2000;Huffman et al, 2001;Miller et al, 2001;Kuligowski, 2002;Kidd et al, 2003;Joyce et al, 2004;Turk and Miller, 2005).…”