Global Drought Monitoring Service through the GEOSS Architecture ...

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Architectural Implementation Pilot, Phase 3 Version: 2.0 Global Drought Monitoring and European Drought Observatory-Water SBA Engineering Report Date: 11/Feb/2011 downscale the reanalysis, which is available at high temporal resolution, and at the same time remove biases in the reanalysis. This work is described in detail in Sheffield et al. (2006). 2.5.1.2 Bridging the gap between reanalysis data and real time observing system data To bridge the data gap between the beginning of 2001 and near-real-time, these methods were extended to blend reanalysis with available observations. Although reanalysis data are available up to real-time, most observation-based datasets are generally only available some months of even years behind real-time. Therefore for 2001-realtime we have used a number of different datasets depending on their availability. For 2001-2006, we have used the recently updated (to 2006) monthly gridded precipitation and temperature dataset of Willmott and Matsura. This matches well the CRU dataset (used for 1950-2000) over their overlap period at large scales. From the beginning of 2007, we have used the Global Precipitation Climatology Project (GPCP) monthly dataset which is available a few months off real-time. Ongoing work is looking at the differences between these various datasets during their overlap periods and methods to ensure temporal consistency. For the last few months up to real-time, we are relying on real-time precipitation products (PERSIANN 20 data from University California Irvine, TRMMM data from NASA) and gauge telemetry (Global Telecommunication System (GTS) gauge data from NOAA). These products are being downloaded on a daily basis and are blended into a forcing dataset for VIC over Africa. Having set the initial meteorological forcing into place, the VIC simulations have been run, up until near-real-time, in order to establish operational running. Our immediate objectives are to finalize the data streams for the real-time running of the VIC model. The rapid timing of real-time operational monitoring creates problems, such as the need to assess whether input data are available, as well as developing fall-back methods for when data are unavailable or fail quality control checks. Furthermore, the real-time meteorological data are likely biased, creating the need to periodically re-run the VIC model up to a few months off real-time when the longterm gridded observation-based products (which are our best estimates of precipitation and temperature) are updated, to avoid a drift in the land surface states. The probability distributions of total column soil moisture and runoff for each grid cell and each month constitute the climatology, against which current conditions can be compared. The screening tools account for drought areal extent and duration using concepts adapted from Andreadis et al (2005), which involve a form of spatial cluster analysis to identify drought patterns from gridded model output. Based on the historic analysis, we will establish a set of severity-area-duration thresholds that can be used to screen evolving droughts. Within the real time monitoring framework, we will monitor where drought thresholds are crossed for either soil moisture or runoff. Once the prescribed drought thresholds have been crossed, we will continue to track drought evolution in time (i.e., in subsequent forecasts), until the nowcasts indicate that 20 http://chrs.web.uci.edu/research/satellite_precipitation/activities00.html Page 20
Architectural Implementation Pilot, Phase 3 Version: 2.0 Global Drought Monitoring and European Drought Observatory-Water SBA Engineering Report Date: 11/Feb/2011 the drought has dissipated. Drought dissipation will be evaluated in comparison with severityarea-duration thresholds estimated using an approach similar to the one used to establish drought screening thresholds. 2.6 New Projects Permitting Further Development of the Global Drought Monitoring Service 2.6.1 European Framework (EF) Drought Early Warning System for Africa-- DEWFORA Under the European Framework, the Drought Forecasting and Early Warning System for Africa (DEWFORA) project has been funded to set up a regional drought monitor for Africa. DEWFORA also includes local and regional pilot projects. This is the reason why DEWFORA is listed in parallel with the Princeton African drought monitor. Figure 2 DEWFORA study regions (Werner et al 2010) 2.6.2 GLOWASIS (Global Water Scarcity Information Service) GLOWASIS will combine in-situ, satellite derived and statistical data on water supply and demand and make them available through a public information portal on water scarcity. Funded under the European FP7 framework, the overall objective is to pre-validate a GMES (Global Monitoring for Environment and Security) Service for Water Scarcity information, based on pilot studies in Europe, Africa and on global level. The main objectives are: • Assessment of water demand and supply Page 21
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