Recent Flooding in the Huntsville Forecast Area and Use of the SPoRT LIS

We have another flooding event upon us at NWS Huntsville, giving 9 straight days now with measurable precipitation.  Moderate flooding is occurring or forecast along some of the Tennessee River tributaries such as the Big Nance and Paint Rock Rivers and minor flooding along the Tennessee River.  Over 5 inches of precipitation have been measured at the Huntsville International Airport during this time, while amounts around 6 to as much as 10 inches of rainfall have been reported or estimated by regional radars in some areas.  This type of rain can often lead to flooding here in the Tennessee Valley, but even heavier precipitation has fallen in the past with barely any flooding.  Such was the case with the passage of the remnants of Tropical Storm Lee across the area in early September 2011.  One of the important factors to consider when assessing the potential for flash flooding or areal flooding is antecedent soil moisture conditions.  Historically, this has been difficult to do, and forecasters often have to make estimates based largely on in-situ observations from very few sites, or from anecdotal evidence and subjective experience.  This is the reason the SPoRT LIS has become a popular tool with forecasters, particularly in the past year, when trying to assess flooding potential.  As early as the 4 am discussion on January 8th, preceding the prolonged heavy rain event, forecasters noted that “the NASA LIS indicates that soil moisture [values] are already fairly high…”.

The SPoRT LIS images below show the 0-10 cm relative soil moisture (Image 1) and the 0-200 cm relative soil moisture (Image 2) on the morning of the 7th (which would have been the latest imagery available to forecasters at the time).

Figure 1. SPoRT LIS 0-10 cm relative soil moisture, valid Jan 7, 2013 0700 LST

 

 

 

 

 

 

 

 

 

Figure 2. The SPoRT LIS 0-200 cm relative soil moisture valid Jan 7, 2013 0700 LST

 

 

 

 

 

 

 

 

 

 

 

Notice that relative soil moisture values (wilting vs saturation point) in the 0-10 cm layer exceeded 60 percent across much of the area.  In the deeper 0-200 cm layer, values exceeded 65 percent across a large portion of the area.  Using these data so far (and this is still subject analysis at this point), forecasters have noticed that when values exceed about 60% and the area receives a “standard” 1-3 inch synoptic rainfall event, flooding issues often arise.   SPoRT LIS soil moisture values were referenced in the Area Forecast Discussion Product not only on the morning of the 8th, but also on the morning of the 9th and the afternoon of the 12th.  These data are quickly becoming a valuable situational awareness tool for forecasters here at the Huntsville NWS office.  Not only are the soil moisture values being used to assess flood potential, but also for drought monitoring and local modeling efforts.  For future efforts, we hope to work with the SPoRT team to conduct more case studies, and determine thresholds based on proper objective analysis.

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Real-time SPoRT/LIS upgraded on September 10th

Effective 10 September, the real-time SPoRT-LIS running over much of the southern and eastern U.S. was upgraded with several improvements.

The upgrade is transparent to Environmental Modeling System (EMS) end-users, since file and data formats are the same and the EMS processing with the “lis” land surface model (LSM) option operates the same as before.  However, it is highly recommended that EMS end-users currently running the “lis” option consider changing to the land-use database described in the 2nd bullet below.

The most noteworthy modifications and improvements are:

• Updated LIS software to support an upgrade from Noah LSM version 2.7.1 to version 3.2.  This upgrade includes an improved look-up table methodology for some static fields and improved handling of heat fluxes over snow-covered regions.
• Changed land-use classification (vegetation type) from the U.S. Geological Survey (USGS) 24-class database to the newer International Geosphere Biosphere Programme (IGBP)/MODIS 20-class database.  The IGBP/MODIS database is more up-to-date than the USGS database, especially with urban classifications.
• Switched from a coarse-resolution surface albedo climatology to a look-up table methodology for surface albedo based on (a) input Green Vegetation Fraction (GVF) data from the high-resolution SPoRT-MODIS real-time product and (b) the newer IGBP/MODIS land-use database.  A sample real-time SPoRT-MODIS GVF map projected onto the 3-km LIS domain is given in Figure 1, showing a comparison between the monthly climatological GVF and the real-time MODIS GVF data from 30 August.  An example comparison between the original climatological specification of surface albedo and the newer look-up table methodology using real-time SPoRT-MODIS vegetation data is given in Figure 2 from the same day.  Both of these upgrades will improve the surface energy budget in the real-time LIS.
• Modified the long-term atmospheric forcing (excluding precipitation) that drives the LIS-Noah LSM integration from the North American Land Data Assimilation System (NLDAS) to NLDAS phase 2 (NLDAS-2).

Contact SPoRT for the official upgrade documentation for further details.

Figure 1. Comparison between the default monthly climatological Green Vegetation Fraction (GVF, in percent) time-interpolated to 30 August (left), and real-time SPoRT-MODIS GVF on 30 August 2012 (right). Note the much lower GVF over the Midwest in the SPoRT-MODIS dataset corresponding to the substantial drought. (Click image twice for full size)

Figure 2. Comparison between climatological surface albedo (%) time-interpolated to 30 August in the former LIS configuration (left), and surface albedo as a function of the real-time SPoRT-MODIS GVF in the upgraded LIS configuration (right). Note the higher surface albedo corresponding to lower SPoRT-MODIS GVF in the Plains and Midwest regions. (Click image twice for full size)

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Collaborative Modeling Project Underway at NWS Huntsville

For the past year, the SPoRT modeling team has been collaborating with the Mobile and Houston NWS Offices, incorporating SPoRT datasets such as the near real-time MODIS green vegetation fraction (GVF), Land Information System (LIS) soil moisture, and SPoRT SSTs into their local WRF EMS model.  Using the Model Evaluation Tools (MET) developed by the National Center for Atmospheric Research, objective verification is being conducted to compare model performance with SPoRT datasets versus that of a control configuration without SPoRT data.  SPoRT has developed a set of scripts that interface with MET and the WRF EMS output to generate objective verification statistics.  The improvement in some forecast parameters due to the use of the high-resolution SPoRT datasets have been documented in previous studies.  The collaborative modeling efforts are still ongoing with the Houston and Mobile offices.

Figure 1. 9 km domain from Huntsville WRF EMS. Parameter shown is precipitable water (inches) valid 06Z 23 August 2012. (click for larger image)

The Huntsville NWS office has entered into a new and similar collaborative phase with the SPoRT modeling team.  The Huntsville WRF EMS model is configured with a 9 km outer domain (shown in Figure 1) encompassing much of the southeastern U.S. and a part of the Ohio Valley and Midwest regions.  A 3 km resolution nested domain contains much of the Tennessee Valley region (Figure 2) and covers a slightly larger area than the previous WRF EMS local run at NWS Huntsville.  The model produces ”standard” output parameters such as temperature/height/wind at 2m, 925mb, 850mb, 700mb, 500mb, and 250mb out to 36 hours.  However, other output  includes (but is certainly not limited to) composite reflectivity, SBCAPE, SBCIN,  0-3 km SR Helicity, 0-1 km shear vector, and precipitable water.  In addition, forecast soundings are produced for eight geographically diverse points within the forecast area.

Figure 2. 3 km nested domain from Huntsville WRF EMS. Forecast parameters shown are 2 meter temperatures (contoured) and 2 meter dew point temperatures (shaded) valid at 06Z 23 August 2012. (click for larger image)

Data and imagery are currently output to an internal web page for forecasters to use operationally, but model output files in grib-2 format will also make data and imagery available for inclusion in AWIPS II in the near future.  Due to the recent acquisition of a new modeling workstation with enhanced computing capability, NWS Huntsville will be able to run both experimental and control forecasts in real-time, with and without SPoRT datasets, respectively.  This will ensure a clean comparison of verification statistics from model runs made on the same computational platform, all performed in-house.  During this collaborative research period, we will be working with the SPoRT modeling team and using the MET tools to objectively determine model performance utilizing SPoRT datasets.

Figure 3. WRF EMS sounding for Huntsville, AL valid 21Z 23 August 2012. The inclusion of SPoRT datasets are expected to have positive impacts on near-surface heat and moisture fluxes, leading to improvements in the model forecast boundary layer temperature and dew point profiles.

With the inclusion of the SPoRT datasets, we expect to see improvements in the model’s handling of surface heat fluxes and associated improvements in low-level temperature/moisture fields and instability parameters.  In the future, we plan to do some case studies evaluating the experimental and control runs.  Using the SPoRT scripts and MET, this can be done in an objective manner in near real-time.

 

Thanks to Jon Case and Andrew Molthan of SPoRT for their help with this post.

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SE CONUS 3-km LIS Imagery are Now Available Online…

Figure 1. Column-integrated (0-200 cm) Relative Soil Moisture, SPoRT 3 km LIS SE CONUS domain at 0600Z July 19, 2012

 

The SPoRT modeling group has been producing a 3 km LIS over the SE CONUS and adjacent areas stretching into the Great Lakes and Great Plains for about two years now.  These data have been made available to collaborative NWS offices through the Southern Region LDM during that time.  However, imagery from the 3 km LIS runs are now being made available through the SPoRT web page.

http://weather.msfc.nasa.gov/sport/

From the SPoRT home page, mouse over the “Core Projects” menu and select the Modeling link.  In the page that opens select real-time AL data or real-time SEUS data in the Real-time Land Information System menu box near the top right.  For convenience, here is a more direct link to the SE CONUS graphics…  http://weather.msfc.nasa.gov/sport/case_studies/lis_SEUS.html

To see more information about the SPoRT LIS, follow this URL… http://weather.msfc.nasa.gov/sport/modeling/lis.html

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From Famine to Feast…

Here in northern Alabama we have gone from very dry and severe drought conditions to a surplus of rain recently.  To see this, take a look at relative soil moisture changes over the last week.  The first image is the 0-10 cm relative soil moisture valid this morning at 4 am CDT.

Figure 1. LIS 0-10 cm relative soil moisture valid 4am CDT July 13 2012.

Now. take a look at values at the end of the oppressive heat wave that brought days of 100F+ temperatures to the area and little to no rainfall.  The graphic below depicts the same soil moisture conditions on the morning of July 5th.

Figure 2. LIS 0-10 cm relative soil moisture valid 4am CDT July 5th 2012.

Significant changes can even be observed in the 0-200 cm integrated-relative soil moisture.  The plot below shows changes over the one week period ending at 4 am CDT this morning.

Figure 3. LIS weekly difference of column integrated (0-200 cm) relative soil moisture ending 4 am CDT July 13 2012.

These plots will continue to be very useful when assessing soil moisture for input to the U.S. Drought Monitor next week.

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T.S. Debby moistening up Florida soils

Tropical Storm Debby in the Gulf of Mexico has generated very heavy rainfall across Florida, especially the western portion of the peninsula.  Rainfall amounts have exceeded 10 inches in spots, according to the 1-week rainfall estimate from the Stage IV analysis valid today (FIG. 1).  This rainfall has led to substantial increases in the available soil moisture across Florida.  The column-integrated relative soil moisture shown in FIG. 2 depicts the ratio of the volumetric soil moisture between the wilting and saturation points through the whole 2-meter soil column.  The plot is derived from the real-time SPoRT Land Information System (LIS) running the Noah land surface model over the southeastern U.S. at 3-km grid spacing.  The Stage IV analysis provides the precipitation input for the LIS-Noah integration.  The relatively moist regions are given by the shades of green across western Florida, parts of south Florida, far southern Mississippi and Alabama, and along the Appalachians into the northeastern U.S.  The 1-week change in the column relative soil moisture illustrates the more recent occurrence of soil moistening over Florida (FIG. 3).  The rainfall from T.S. Debby has increased the column relative soil moisture by 10-20% or more within the past week (much of it in the last day or two).   Since Florida has a predominantly sandy soil type that recharges quickly, soils can moisten rapidly from a significant rain event.  Conversely, a period of dry weather with intense surface heating can dry out sandy soils very quickly.

Figure 1. One-week precipitation estimate from the Stage IV analysis (in inches) for the week ending 25 June 2012.

Figure 2. Column-integrated relative soil moisture valid at 0900 UTC 25 June 2012, derived from the real-time SPoRT LIS running the Noah land surface model.

Figure 3. One-week change in the column-integrated relative soil moisture, valid for the week ending 0900 UTC 25 June 2012.

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Follow-up to HWT CI Event in TX Panhandle: Radar Loop

The figure below shows a radar loop of the supercell for 1.5 hours leading up to the time of the tornado.  Notice how the supercell to the WNW of Amarillo, TX develops nearly in place, along the NW edge of the moist soil patch as documented in the previous blog post on this topic.  Prevailing low-level flow was from the SE, which may have led to maximum convergence to the NW of the moist patch, given a “sea breeze-like” circulation due to differential surface heating.  I plan to make some WRF model simulations using the NASA Land Information System to further explore the role of soil moisture patterns in developing the convection in west Texas on this day. (Click twice on the image below to see the radar animation.)

FIG 1. One and a half hour animation of base reflectivity over the Texas Panhandle, valid from 0000 UTC to 0130 UTC 22 May 2012.  Credit: Plymouth State University Weather Center web page.

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Convective Initiation Event during the HWT Experimental Forecast Program

It’s Jonathan Case reporting from the Hazardous Weather Testbed (HWT) Experimental Forecast Program (EFP) in Norman, OK.  At the EFP this year, teams of researchers and operational forecasters are coming together to examine cutting-edge, convection-allowing ensemble numerical model output, unique diagnostic model fields, and experimental observation platforms to forecast convective initiation and severe weather events.  Each day, the participants are divided into sub-groups with one group forecasting severe weather over a pre-selected focus region while the other group forecasts convective initiation and coverage in the same general sub-domain.

On Monday, the focus region was over eastern New Mexico and the Texas Panhandle.  Model guidance was pretty good at indicating storms developing over the higher terrain of NM, and then conglomerating into a SE-moving mesoscale complex over the TX Panhandle after 00z 22 May. During verification activities Tuesday morning, an interesting feature was seen in the visible satellite imagery over the western Texas Panhandle in the afternoon and early evening hours.  A small area had a dearth in cumulus cloud development a little east of the NM border, as highlighted in FIG 1.  At the time of the visible image in FIG 1 (2245 UTC), convective storms began developing on the NW edge of this cloud-free “patch”, ahead of the developing convection in NM.  This convection intensified with time, as seen in the radar image in FIG 2.  In fact, a tornado was reported at 0137 UTC 22 May not far from this location (http://www.spc.noaa.gov/climo/reports/120521_rpts.html), as the convection on the NW side of the “patch” continued to intensify into an isolated supercell over the next 2 hours (not shown).

FIG 3 is a 500-meter true-color image from MODIS, centered over the TX Panhandle at 1729 UTC 21 May, before cumulus cloud development occurred on the periphery of the “patch”.  One can distinctly see the darker brown color of the “patch” compared to the lighter brown color of the surrounding landscape.  Further investigation reveals that the darker brown color of the “patch” correlated very well with high antecedent rainfall from the previous day (FIG 4; 24-hour rainfall of ~0.5″ to 2.0″, ending the morning before the event of interest).

What likely happened is that the previous day’s rainfall moistened the top soil layer over this patch, thereby reducing the overall surface albedo making the land surface appear darker in the MODIS true color image.  Because more incoming shortwave energy was partitioned into evaporating soil moisture, the surface heated more slowly than the surrounding landscape.  This differential heating appears to have led to a small-scale “sea-breeze-like” circulation, enhancing the cumulus cloud development on the periphery of the moist patch by late afternoon.  Additional research is required to determine whether this moist patch ultimately contributed to the tornado occurrence.

FIG 1. GOES visible satellite image at 2245 UTC 21 May 2012. Red label indicates location of patch where a lack of cumulus cloud development occurred.

FIG 2. Base reflectivity image over the Texas Panhandle at 2259 UTC 21 May 2012. Red outline indicates the convective cell developing on the NW edge of the cloud-free patch.

FIG 3. MODIS true color image at 500 m resolution, centered on the Texas Panhandle, valid at 1729 UTC 21 May 2012.

FIG 4. Stage IV precipitation analysis over the Amarillo, TX WFO county warning area for the 24-hour period ending 1200 UTC 21 May 2012.

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The NASA 1km LIS and Recent Applications for the U.S. Drought Monitor

In addition to being the Applications Integration Meteorologist for the NASA SPoRT program, I have retained my climate focal point duties at NWS Huntsville, AL.  As a part of those duties, each week, I am honored to be able to provide feedback to the U.S. Drought Monitor (USDM).  The USDM consists of a consortium of academic and government partners, including the University of Nebraska-Lincoln National Drought Mitigation Center (NDMC) and various agencies under NOAA and the USDA.  Responsibility for ultimate authorship of the USDM each week falls to a rotating reponsibility of drought specialists within the various agencies and the UN-Lincoln NDMC.  Each new week presents new challenges, particularly when assessing potential impacts due to low streamflow or low soil moisture for various parts of the country.  Last week saw the introduction of D1 (moderate) drought conditions across portions of northern Alabama and southern middle Tennessee due to continued lack of rainfall and degradation of soil moisture and streamflows.  This week, however, presented a new set of challenges, as parts (but certainly not all) of the area received some beneficial rainfall.  This is depicted well in the in the 7-day Stage-IV precipitation map shown below.

Figure 1. Stage-IV Precipitation for northern AL and adjacent areas for the 7-day period ending May 8th, 2012. The scale is on the left. Notice that amounts ranged from around 0.25 inch in the northeast to around 3-4 inches in the parts of the west. Normal weekly rainfall for this time of year is around 1.25 inches.

As shown in Figure 1 above, rainfall was just around one quarter of an inch in portions of northeast Alabama, with amounts rising to around 2 to as much as 4 inches mainly in southwest portions of the Huntsville CWA, especially parts of Cullman, Franklin, and Colbert Counties.  The image below shows precpitation anomalies for the same 7 day period.

Figure 2. Stage-IV Precpitation Anomalies for the 7-Day Period Ending May 8th 2012. (Note: anomalies are based on the 1971-2000 normals period. Values are in units of inches (the scale is to the left.)

As figure 2 above shows, precipitation was generally below normal for the week in portions of northeast Alabama, but was a little above normal in southern parts of our forecast area…with near normal precipitation in between.  Since the USDM is updated on a weekly basis (Tuesday 12z – Tuesday 12z), the typical concerns involve how much precipitation fell during the weekly period and how this affected soil moisture and the hydrologic system.  As meteorologists, we usually have a fairly good sense of rainfall amounts.  However, we are often unsure how the soil and hydrologic systems respond to these inputs because there are so many factors to consider (runoff vs infiltration, evapotranspiration rates, etc).  Additionally, these changes can be challenging to assess due to a general lack of in-situ observations.  In northern Alabama, we are blessed with several soil moisture sensors as a part of the USDA Soil Climate Analysis Network (SCAN).  However, this network is still relatively sparse for the purposes of drought monitoring, especially when decisions have to be made on sub-county scales.  This is why the NASA LIS 1km domain over Alabama can be such a useful situational awareness tool for the purposes of drought monitoring.  Indeed, such was the case just this week.  While rainfall amounts ranged from slightly below normal to slightly above normal across the area, the question begging was…”how did the soil moisture respond to these inputs?”  Did evaporation and evapotranspiration exceed the inputs to the system in western and southern areas?  Or was it the converse?  How about the lack of rainfall in the northeast.  Were evaporation and evapotranspiration rates sufficiently low there so that the impact to soil moisture was minimal?  These are questions that often need to be answered for weekly feedback to the USDM.  After assessing rainfall amounts, a quick look at streamflows through the USGS WaterWatch site showed that they were still depressed after recent rains.  So, now on to the 1km soil moisture assessment and the Alabama domain maps available through the NASA SPoRT web site (these are also available through the Southern Region LDM and AWIPS).  The 0-10 cm soil moisture percentage quickly helped me to key in on areas where recent deficiencies were present, as shown below.

Figure 3. NASA LIS 0-10 cm relative soil moisture valid May 8th, 2012 0600Z. DeKalb and Marshall Counties are highlighted for the purposes of this post. Notice the low soil moisture in portions of southern DeKalb County and adjacent areas of Marshall County.

The What was quickly apparent was the relatively low soil moisture values in southern portions of DeKalb County and adjacent areas in eastern Marshall County, AL.  Notice there, that values were similar to those in portions of central and southern Alabama (albeit on a smaller scale) where D1 or worse conditions existed in some places.  These shallow (0-10 cm) soil moisture values will be the most responsive, of course, to short term rainfall anomalies.  So, seeming shortages in soil moisture existed in portions of northern Alabama.  So, the next question was…”how has this changed since last week?”  Some rain had occurred, but was it enough to increase the soil moisture values.  This is where the one-week change maps come into play, as shown in figure 4 below.

Figure 4. NASA LIS 1 km 0-200 cm integrated relative soil moisture weekly difference, valid May 8th, 2012 0900Z.

Notice in the above weekly difference plot that despite rainfall over the past week, soil moisture values decreased mainly across portions of northern and northeastern AL.  Since soil moisture values already were lower in portions of southern DeKalb County than in other areas, then it seemed as though they were a likely candidate for expansion of the D1 (moderate) drought conditions that had been introduced in parts of the area last week.  Essentially, the LIS had helped me to focus in on a particular area very quickly, reducing the investigative work that often goes into these types of assessments.  As a result of the coupling of the Stage-IV data and the LIS soil data, I spoke with an Agricultural Extension Specialist at the Sand Mountain Research and Extension Center in Crossville, AL.  He verified that crops in the area in question in southern DeKalb County were indeed under stress due to the low soil moisture, in addition to a couple of recent frosts.  With all of this information at hand, the recommendation was made to the author of the drought monitor to extend D1 (moderate) drought conditions into this portion of the area.  Because the integrated soil moisture difference plots indicated relatively minor improvement to areas that received rainfall this past week, and considering longer-scale (14-60 day) precipitation deficits and low soil moisture, drought designations were kept status-quo in other parts of the area for now.

By the way, I can’t post the latest draft of the USDM, but will post the official due out tomorrow morning.  Due to the evidence provided by the NASA LIS and direct input from an extension specialist from the ACES, the D1 was extended into the areas recommended.

UPDATED – May 10th

Okay, as promised, here is the latest USDM for the state of Alabama…

Figure 5. U.S. Drought Monitor for Alabama, May 8th 2012.

Notice the area of moderate drought (D1) was extended southward through portions of DeKalb and Marshall Counties that were mentioned above.  This may seem rather insigificant to those who aren’t familiar with the USDM and the types of decisions that go into this process.  However, delineating these boundaries properly is important, especially for those (and the counties) that may be affected.  Drought designations have implications particularly for agriculture and whether or not federal help is necessary to assist agricultural producers.  The NASA LIS has been an invaluable tool in helping me to assess impacts due to lack of precipitation in the northern Alabama area.

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SPoRT/MODIS Real-time Vegetation Depicts Early Green-up

March 2012 was a month for the climatological record books, with anomalously warm temperatures prevalent across much of the Contiguous United States.  Numerous stations recorded their all-time warmest March mean temperature, including the greatest departure above normal for any month.

These unusually warm temperatures translated into an early, rapid green-up in the deciduous vegetation across much of the eastern half of the United States.  This rapid green-up is captured well by the real-time SPoRT/MODIS vegetation product, which is produced once per day at 0.01° resolution over the U.S. lower 48 states and adjacent portions of southern Canada and northern Mexico.  The figure below shows a one-year change in the SPoRT/MODIS Greenness Vegetation Fraction (GVF) product from 2011 to 2012, valid on 11 April.  Most of the eastern U.S. has larger GVF than last year by 10% or more.  In fact, a significant part of southeastern Canada has GVF increases over 40% compared to last year.  Parts of the Tennessee / Mississippi river valleys, and New England also have year-to-year increases of comparable magnitude.

Such dramatic inter-annual changes in the health and coverage of green vegetation can have significant impacts on the surface energy budget within numerical weather prediction models.  The default vegetation dataset in community models such as the WRF model consists of a climatology that depicts vegetation coverage the same from year to year.  In anomalous situations such as this Spring, the climatological dataset would likely mis-represent the coverage of vegetation in the model, thus negatively affecting the energy exchanges between the land surface and planetary boundary layer.  Therefore, the use of real-time vegetation, such as the SPoRT/MODIS product, has the potential to better represent vegetation coverage and the subsequent surface energy budget in real-time models.

One-year change in SPoRT/MODIS real-time Greenness Vegetation Fraction (GVF) from 11 April 2011 to 11 April 2012.

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