• Arkin, P. A., 1979: The relationship between fractional coverage of high cloud and rainfall accumulations during GATE over the B-scale array. Mon. Wea. Rev.,107, 1382–1387.

  • Barrett, E. C., and D. W. Martin, 1981: The Use of Satellite Data in Rainfall Monitoring. Academic Press, 340 pp.

  • Doswell, C. A., III, R. Davies-Jones, and D. L. Keller, 1990: On summary measures of skill in rare event forecasting based on contingency tables. Wea. Forecasting,5, 576–585.

  • Ebert, E. E., 1995: Results of the Third Algorithm Intercomparison Project (AIP-3) of the Global Precipitation Climatology Project (GPCP). Bureau of Meteorology Research Centre, Melbourne, Australia. [Available from BMRC, GPO Box 1289K, Melbourne 3001, Australia.].

  • Grassotti, C., and L. Garand, 1994: Classification-based rainfall estimation using satellite data and numerical forecast model fields. J. Appl. Meteor.,33, 159–178.

  • Guymer, T. H., J. A. Businger, W. L. Jones, and R. H. Stewart, 1981:Anomalous wind estimates from the Seasat scatterometer. Nature,294, 735–737.

  • Hoffman, R. N., 1984: SASS wind ambiguity removal by direct minimization. Part II: Use of smoothness and dynamical constraints. Mon. Wea. Rev.,112, 1829–1852.

  • Negri, A. J., and R. F. Adler, 1987: Infrared and visible satellite rain estimation. Part I: Grid cell approach. J. Climate Appl. Meteor.,26, 1553–1564.

  • Smith, D. K., and F. J. Wentz, 1998: NSCAT wind retrieval within high rain events. Extended Abstracts, American Geophysical Union Spring Meeting, Boston, MA, Amer. Geophys. Union. [Available online at http://www.agu.org.].

  • Smith, E., and Coauthors, 1998: Results of WetNet PIP-2 project. J. Atmos. Sci.,55, 1483–1536.

  • Spencer, M., and M. Shimada, 1991: Effect of rain on Ku-band scatterometer wind measurements. Proc. Int. Geoscience and Remote Sensing Symp. (IGARSS ’91), Espoo, Finland, IEEE, 1285–1288.

  • Velden, C. S., and T. L. Olander, 1998: Bispectral satellite technique for delineating intense convection: Applications to tropical cyclones. Preprints, Ninth Conf. on Satellite Meteorology and Oceanography, Vol. 2, Paris, France, Amer. Meteor. Soc. 458–461.

  • Wentz, F. J., 1992: Measurement of oceanic wind vector using satellite microwave radiometers. IEEE Trans. Geosci. Remote Sens.,30, 960–972.

All Time Past Year Past 30 Days
Abstract Views 0 0 0
Full Text Views 163 5 0
PDF Downloads 11 1 0

Development and Application of a Visible–Infrared Rain Flag for Scatterometer Data

View More View Less
  • 1 Atmospheric and Environmental Research, Inc., Cambridge, Massachusetts
Restricted access

Abstract

The authors report on characteristics of a rain flag derived from collocation of visible and infrared image data with rain rates over the North Atlantic Ocean obtained from microwave imagery (SSM/I) during a 3-week period (15 October 1996–2 November 1996). The rain flag has been developed as part of an effort to provide an indication of contamination by heavy rainfall in NASA scatterometer datasets. The primary results of this analysis indicate 1) that a simple albedo/infrared brightness temperature threshold is capable of flagging most of the heavy rainfall, though with a fairly high rate of false alarms, and 2) that the small difference in optimal threshold between the Tropics and midlatitudes can probably be ignored. Use of the rain flag in 12 assimilation experiments during this period showed that the number of rain-flagged wind vector cells is generally less than 1% of the number of cells. Overall, the impact from using the rain-flagged data is generally less than 5 m s−1 and localized (less than 5° of latitude and longitude). However, in some cases, the effect of excluding just one to five rain-flagged points can change the resulting analysis significantly, because their placement is critical for defining the flow along a front or some other shear-dominated environment.

Corresponding author address: Christopher Grassotti, Atmospheric and Environmental Research, Inc., 840 Memorial Drive, Cambridge, MA 02139.

cgrass@aer.com

Abstract

The authors report on characteristics of a rain flag derived from collocation of visible and infrared image data with rain rates over the North Atlantic Ocean obtained from microwave imagery (SSM/I) during a 3-week period (15 October 1996–2 November 1996). The rain flag has been developed as part of an effort to provide an indication of contamination by heavy rainfall in NASA scatterometer datasets. The primary results of this analysis indicate 1) that a simple albedo/infrared brightness temperature threshold is capable of flagging most of the heavy rainfall, though with a fairly high rate of false alarms, and 2) that the small difference in optimal threshold between the Tropics and midlatitudes can probably be ignored. Use of the rain flag in 12 assimilation experiments during this period showed that the number of rain-flagged wind vector cells is generally less than 1% of the number of cells. Overall, the impact from using the rain-flagged data is generally less than 5 m s−1 and localized (less than 5° of latitude and longitude). However, in some cases, the effect of excluding just one to five rain-flagged points can change the resulting analysis significantly, because their placement is critical for defining the flow along a front or some other shear-dominated environment.

Corresponding author address: Christopher Grassotti, Atmospheric and Environmental Research, Inc., 840 Memorial Drive, Cambridge, MA 02139.

cgrass@aer.com

Save