Showing papers in "Earth Interactions in 2002"

Interpretation of TRMM TMI Images of Tropical Cyclones

Abstract: Images of the 85-GHz frequency from the Special Sensor Microwave Imager (SSM/I) aboard the Defense Meteorological Satellite Program (DMSP) spacecraft are routinely viewed by forecasters for tropical cyclone analyses. These images are valued because of their ability to observe tropical cyclone structure and to locate center positions. Images of lower-frequency SSM/I channels, such as 37 GHz, have poor quality due to the coarse spatial resolution, and therefore 85 GHz has become the de facto analysis standard. However, the Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI), launched in 1997, has much better spatial resolution for all channels than the SSM/I. Although originally designed to investigate precipitation for climate research, real-time images are now sent into tropical cyclone forecast offices, and posted to Web pages of the Naval Research Laboratory and the Fleet Numerical Meteorology and Oceanography Center, both in Monterey, California. TMI images of 37 GHz have a numbe...

Relative Importance of the Annual Cycles of Sea Surface Temperature and Solar Irradiance for Tropical Circulation and Precipitation: A Climate Model Simulation Study

Abstract: A recent version of the Goddard Earth Observing System GCM which contains several upgrades to the model's prognostic cloud physics and microphysics as well as snow and ice hydrology, was used to isolate the influences of the annual cycles of solar irradiation and sea surface temperatures (SSTs) on the annual cycle of circulation and precipitation. Four 50-month-long integrations were produced with the GCM. The first integration, called the control simulation, C, was forced with daily interpolated SSTs from a 30-yr climatology of monthly SST data. In this simulation both SSTs and incoming solar irradiance had their normally prescribed annual cycles. The next two companion simulations were called S1, which used annual mean prescribed incoming solar irradiation, and S2, which used annual mean prescribed SST; everything else was kept similar to C in these two simulations. In the fourth simulation, called S3, both SSTs and incoming solar irradiation at the top of the atmosphere were prescribed to alwa...

Analysis of a Mesoscale Gravity Wave Event Using Empirical Orthogonal Functions

Abstract: A method is detailed that filters mesoscale gravity wave signals from synoptic-level observation data using empirical orthogonal functions (EOFs). Similar EOF analyses have been used to study many oceanographic and meteorological features by allowing the examination of the variance associated with the principal orthogonal components of a time series in both spatial and temporal formats. Generally, EOF components are tied only to the underlying physical phenomena driving the observations when they represent a significantly large portion of the cumulative EOF variance. This work demonstrates a case in which a physically significant gravity wave event is recovered from the synoptic signal using EOF components that represent a small percentage of the total signal variance. In this case this EOF filtering technique appears to offer several advantages over more traditional digital filtering methods; namely, it appears to capture more of the gravity wave amplitude, it requires less preconditioning of th...