# Presentation: 113863

## SeaWiFS Views Turbid Water 

**Along the Carolina–Georgia–Florida Coast**
- Gene Feldman, NASA GSFC, Laboratory for Hydrospheric Processes, Office for Global Carbon Studies (_[gene.c.](mailto:gene.c.feldman@nasa.gov)__[feldman](mailto:gene.c.feldman@nasa.gov)__[@](mailto:gene.c.feldman@nasa.gov)__[nasa](mailto:gene.c.feldman@nasa.gov)__[.](mailto:gene.c.feldman@nasa.gov)__[gov](mailto:gene.c.feldman@nasa.gov)_)
- On Saturday, February 28, 2004, SeaWiFS viewed an area of very turbid water along the coasts of the Carolinas, Georgia, and Florida, which is usually an indication of high winds. The weather map (right) of early Saturday morning, confirmed that the south-eastern U.S. had fairly brisk winds.  The highest wind speed is listed over Georgia  in the 48–52 knot range.  Such winds can generate considerable wave action which resuspends continental shelf sediments and gives the water the turbid appearance seen in the SeaWiFS image.
- Other features of note in the image include the fingers of very dark water around Suwannee Sound and Apalachee Bay in northwestern Florida. The river water flowing into these coastal areas is known to contain dissolved colored organic material.  The white patch over the Carolina piedmont region is snowfall.  Snowfall is also visible farther north and ice covers much of Lake Erie and Lake St. Claire.

## Slide 2

## GRACE Satellites Provide First Space-Based Observations of Terrestrial Water Storage

***Matthew Rodell****, Jianli Chen, Sally Holl, Jay Famiglietti, Clark Wilson*
**NASA GSFC, Laboratory for Hydrospheric Processes, Hydrological Sciences Branch**
**(Matthew.Rodell@nasa.gov)**
**Background**
- The twin satellites of the Gravity Recovery and Climate Experiment (GRACE) were launched on 17 March 2002 with the goal of generating a new, global map of Earth's gravity field every month.  The high precision of the GRACE measurement technique enables observation of slight gravitational variations. Over land, gravitational variations are caused mainly by the cycling of terrestrial water and atmospheric mass.  We can predict atmospheric circulation reasonably well using numerical models, so that its contribution to the gravity (and, thus, mass) changes observed by GRACE can be subtracted from the measured fields.  This results in the first-ever space-based maps of variations in terrestrial water storage (groundwater, soil moisture, snow, ice, and surface water).
**Objective and Method:**
- Here we compare terrestrial water storage (TWS) variations derived from GRACE with those estimated by the Noah land surface model running offline (not coupled to the atmosphere) within NASA/GSFC’s Global Land Data Assimilation System (GLDAS).  GLDAS generates high resolution fields of land surface states (e.g., snow, soil moisture, temperature) and fluxes (e.g., evaporation, runoff) in near real-time, relying largely on observation-based meteorological products for forcing (input).  The comparison provides a form of validation for both the GRACE and GLDAS products.  In other words, if the products are similar, it is likely that GRACE truly “sees” TWS variations and that the GLDAS output is realistic.
**Results and Discussion:**
- GRACE-derived TWS anomalies (variations from the mean) are compared with modeled soil moisture plus snow anomalies in the following two figures.  The first figure presents global maps of TWS anomalies (cm equivalent height of water) from GRACE and GLDAS, for April and September, 2003.  Both products were effectively smoothed to a 2000 km length scale, which explains any color variations over the oceans.  The agreement is strong, with corresponding highs and lows across parts of Europe, Africa, southeast Asia, and South America.  The contrast of the spring and autumn anomalies hints at the annual cycling of water through these regions.  The panels in the second figure plot the TWS anomaly (cm) versus latitude for each of the eleven months for which GRACE has produced a global gravity map.  In addition to GLDAS, a second set of land surface model based soil moisture plus snow estimates is included for comparison, from NOAA’s Climate Prediction Center (CPC).  Overall the agreement between the models and GRACE is good, and GLDAS output generally compares more favorably than CPC output.

## Comparison of GRACE-Derived Terrestrial Water Storage with Modeled Soil Moisture + Snow

**Comparison of GRACE-Derived Terrestrial Water Storage with Modeled Soil Moisture + Snow**

## Comparison of GRACE-Derived Terrestrial Water Storage with Modeled Soil Moisture + Snow

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**Latitude**

**Comparison of GRACE-Derived Terrestrial Water Storage with Modeled Soil Moisture + Snow**

## Surface Reference Technique (SRT) for Estimating Path-Attenuation for the TRMM Precipitation RadarRobert Meneghini, NASA GSFC, Laboratory for Hydrospheric Processes, Microwave Sensors Branch (robert.meneghini@nasa.gov)

- At the TRMM Radar Freq. (13.8 GHz), Path-Integrated Attenuation is Required for Rain Rate Estimation
- For moderate & heavy rains, the SRT is used
- Technique uses rain-free surface cross-sections as a reference for determining precipitation path attenuation along radar beam
- New implementation (hybrid SRT) for version 6 algorithm uses both along-track and cross-track surface scattering information
- Accuracy of method can be checked by comparing estimates from forward and backward processing of the orbit

## Above: Path-Integrated Attenuation as determined by 

***Above***: Path-Integrated Attenuation as determined by
- the hybrid SRT using forward (top) and backward (middle) processing of data and difference (bottom).
***Right-top***: details of the estimation for a single scan using forward processing.
***Right-bottom***: Same but for backward processing.