Recent technology advances in miniature microwave radiometers that can be hosted on very small satellites has made possible a new class of affordable constellation missions that provide very high revisit rates of tropical cyclones and other severe weather. The Time-Resolved Observations of Precipitation structure and storm Intensity with a Constellation of Smallsats (TROPICS) mission was selected by NASA as part of the Earth Venture–Instrument (EVI-3) program and is now in development with planned launch readiness in late 2019. The overarching goal for TROPICS is to provide nearly all-weather observations of 3-D temperature and humidity, as well as cloud ice and precipitation horizontal structure, at high temporal resolution to conduct high-value science investigations of tropical cyclones (TCs). TROPICS will provide rapid-refresh microwave measurements (median refresh rate better than 60 minutes for the baseline mission) over the tropics that can be used to observe the thermodynamics of the troposphere and precipitation structure for storm systems at the mesoscale and synoptic scale over the entire storm lifecycle. TROPICS will comprise a constellation of at least six CubeSats in three low-Earth orbital planes. Each CubeSat will host a high performance radiometer to provide temperature profiles using seven channels near the 118.75 GHz oxygen absorption line, water vapor profiles using three channels near the 183 GHz water vapor absorption line, imagery in a single channel near 90 GHz for precipitation measurements (when combined with higher resolution water vapor channels), and a single channel at 205 GHz that is more sensitive to precipitation-sized ice particles and low-level moisture. This observing system offers an unprecedented combination of horizontal and temporal resolution in the microwave spectrum to measure environmental and inner-core conditions for TCs on a nearly global scale and is a major leap forward in the temporal resolution of several key parameters needed for assimilation into advanced data assimilation systems capable of utilizing rapid-update radiance or retrieval data. Here, we provide an overview of the mission and an update on current status, with a focus on unique characteristics of the Cubesat system, recent performance simulations on a range of observables to be provided by the constellation, and a summary of science applications.
The Atmospheric Infrared Sounder (AIRS), together with the Advanced Microwave Sounding Unit (AMSU), represents
one of the most advanced space-based atmospheric sounding systems. Aside from monitoring changes in Earth's
climate, one of the objectives of AIRS is to provide sounding information with sufficient accuracy such that the
assimilation of the new observations, especially in data sparse regions, will lead to an improvement in weather forecasts.
The combined AIRS/AMSU system provides radiance measurements used as input to a sophisticated retrieval scheme
which has been shown to produce temperature profiles with an accuracy of 1 K over 1 km layers and humidity profiles
with accuracy of 10-15% in 2 km layers in both clear and partly cloudy conditions. The retrieval algorithm also provides
estimates of the accuracy of the retrieved values at each pressure level, allowing the user to select profiles based on the
required error tolerances of the application. The purpose of this paper is to describe a procedure to optimally assimilate
high-resolution AIRS profile data in a regional analysis/forecast model. The paper focuses on a U.S. East-Coast cyclone
from November 2005. Temperature and moisture profiles-containing information about the quality of each
temperature layer-from the prototype version 5.0 Earth Observing System (EOS) science team retrieval algorithm are
used in this study. The quality indicators are used to select the highest quality temperature and moisture data for each
profile location and pressure level. AIRS data are assimilated into the Weather Research and Forecasting (WRF)
numerical weather prediction model using the Advanced Regional Prediction System (ARPS) Data Analysis System
(ADAS), to produce near-real-time regional weather forecasts over the continental U.S. The preliminary assessment of
the impact of the AIRS profiles will focus on intelligent use of the quality indicators, analysis impact, and forecast
verification against rawinsondes and precipitation data.
The hyperspectral resolution measurements from the NASA Atmospheric Infrared Sounder (AIRS) are advancing climate research by mapping atmospheric temperature, moisture, and trace gases on a global basis with unprecedented accuracy. Using a sophisticated retrieval scheme, the AIRS is capable of diagnosing the atmospheric temperature in the troposphere with accuracies of less than 1 K over 1 km-thick layers and 10-20% relative humidity over 2 km-thick layers, under both clear and cloudy conditions. A unique aspect of the retrieval procedure is the specification of a vertically varying error estimate for the temperature and moisture profile for each retrieval. The error specification allows for the more selective use of the profiles in subsequent processing. In this paper, we describe a procedure to assimilate AIRS data into the Weather Research and Forecasting (WRF) model to improve short-term weather forecasts. The ARPS Data Analysis System (ADAS) developed by the University of Oklahoma is configured to optimally blend AIRS data with model background fields based on the AIRS error profiles. The WRF short-term forecasts with selected AIRS data show improvement over the control forecast. The use of the AIRS error profiles maximizes the impact of high quality AIRS data from portions of the profile in the assimilation/forecast process without degradation from lower quality data in the other portions of the profile.
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