Gridded NUCAPS for Anticipating Convection Joint Project between NASA SPoRT, NOAA, CIMSS, CIRA, GINA, and STC Introduction This training module will take you through the steps on how to use the Gridded NUCAPS to increase situational awareness when diagnosing the pre-convective environment. Forecasters will understand: Strengths and weakness of the Gridded NUCAPS Gridded NUCAPS in the forecast process to identify potential areas of convection Hyperspectral Infrared Sounders NUCAPS NOAA Unique Combined Atmospheric
Processing System CrIS Cross Track Infrared Sounder (1305 Channels) ATMS Advanced Technology Microwave Sounder (22 Channels) Onboard Suomi/NPP overpasses between standard radiosonde launch times Passes over East Coast: 05z/17z The Plains: 07z/19z West Coast: 11z/23z Alaska: Multiple Takes advantage of a much larger number of channels (as compared to current GOES, HIRS, legacy TOVS sounders) to better resolve vertical structure in the atmosphere Measure temperature and water vapor with height as well as ozone, other trace gases, and cloud information (e. g. cloud top fraction, cloud top pressure) Most accurate in the upper-levels under clear conditions Infrared and microwave measurements are paired to allow for measurements in partly cloudy regions Measurements are degraded in regions of thick clouds How is a NUCAPS Sounding retrieved? Initial profile statistically derived from MW (ATMS) and
full IR measurement (all channels of CrIS) Perform cloud clearing to remove cloud signal from IR radiance IR spectrum Brightness Temp MW spectrum Physical retrieval using both MW and a subset of cloud-cleared IR channels. This involves - Error checking, diagnostic tests, iteration - Sequential retrieval of T, q, CO, O3, CH4, etc. - Quality flags
Which CrIS channels are used? 399 of them 24 for surface temperature 87 for atmospheric temperature 62 for water vapor Adjacent Channels are not used Channels chosen are predominantly sensitive to one gas only Produce final IR+MW NUCAPS soundings at 100 layers MW-only NUCAPS soundings available operationally but not in AWIPS yet Effective Vertical Resolution of Satellite Soundings CrIS and ATMS can resolve: 4-6 layers of water vapor 6-10 layers of temperature Scene 1 Layers
in the troposphere so think layer values rather than specific point values. How are the layers vertically distributed? it varies from scene to scene and is dependent on Earth surface as well as local weather conditions Vertical Resolution Estimates Images are from Maddy & Barnet, IEEE, 2008 Scene 2 Layers Effective Vertical Resolution of Satellite Soundings So what does this mean in operations? satellite soundings, such as NUCAPS, will have a smoother appearance Radiosonde
NUCAPS Sounding Barrow, Alaska NUCAPS Limitations The amount/quality of retrievable information varies from scene to scene depending on local weather conditions Infrared observations are sensitive to surface temperature Land vs ocean Day vs night Local conditions No single parameter (T, q) is retrieved without interference from others (T, q, trace gases) Cloud cover and edges of clouds Success in cloud cover up to 90% Does not retrieve atmospheric conditions inside/through clouds NUCAPS retrieves atmospheric conditions from clear-sky pathway around clouds Cloud clearing removes the radiative effects of clouds and preserves the clear-sky portion of the foot print or emission signal that reaches the top of the atmosphere What about clouds? To an IR Sounder clouds are an obstacle. A <5% probability that ~50km footprint is cloud-free
NUCAPS performs cloud clearing to increase global yield of soundings, thus soundings are retrieved under most cloud/surface conditions. NUCAPS have spatial + temporal consistency, it also has soundings of atmospheres nearly impossible for radiosondes to reach Nadir Sc an an gle =5 0 NUCAPS does NOT retrieve thermodynamic environment THROUGH clouds n a an c
S gle 0 5 = Nadir NUCAPS retrieves cloud-free thermodynamic environment AROUND/PAST clouds
Uniformly cloudy Uniformly cloudy High optical thickness Low spatial variability Cloud contrast, High spatial variability; NUCAPS retrievals in up to 90% cloudiness Low optical thickness Low spatial variability Cloud Clearing: Use clusters of footprints to remove cloudy signal from radiance measurement Clear sky: high quality IR+MW retrievals (soundings) Partly cloudy: use clear sky CrIS
footprints to perform cloud clearing. Constrained by ATMS Infrared Measurement (CrIS) in clusters of 3 x 3 (~50km at nadir) Microwave measurement (ATMS) averaged to CrIS clusters Uniformly cloudy: retrieval fails and poor quality NUCAPS sounding results Current Operational NUCAPS Visualization NUCAPS is the NOAA Operational Retrieval algorithm for CrIS/ATMS and IASI/AMSU T and q profiles Capabilities for displaying individual Skew-T plots are available in the latest versions of AWIPS II with quality control flags Skew-Ts are valuable for some forecast challenges, and visualizing the data in plan view or cross section may be more
useful for others NUCAPS allows forecasters to observe the 3D extent of the atmosphere where conventional observations are sparse NUCAPS Sounding locations overlaying radar in AWIPS Images by Kris White (NWS HUN/NASA SPoRT) NUCAPS Sounding locations in AWIPS NUCAPS Sounding in AWIPS Gridded Product Overview NUCAPS Data Levels Output from Polar2Grid
0 Stack of individual layers (Temp/SPFH) 100 200 P2G 300 AWIPS NUCAPS Soundings: Need to click on each dot to review the vertical information Pros: Can choose specific locations Cons: A lot of individual
interrogation 58 levels are output using Polar2Grid from the 100 layers output by NUCAPS. Ingested into AWIPS on a uniform model grid, so AWIPS will interrogate the information in the same way it handles model data allowing for plan view and cross sections PressureLevels (mb) 400 500 600 700 800
900 1000 Data Levels in AWIPS 2 NOAA CrIS/ATMS data delivery: Operational (CLASS/SBN) vs Direct-Broadcast (CSPP) FOV = field of view (yellow) FOR = field of regard (blue) Operational NOAA CrIS/ATMS footprints Direct Broadcast NOAA CrIS/ATMS footprints 9 x CrIS FOVs inside 1 x ATMS FOR 7 x CrIS FOVs inside 1 x ATMS FOR
Dotted NUCAPS in AWIPS is delivered via operational SBN stream Gridded NUCAPS in AWIPS is delivered via CSPP/DB stream Two footprints (#4 and #6) are removed from realtime DB stream to decrease data latency IMPACT: We can expect to see a mismatch in quality flags and retrieval quality at the edges of cloud fields between the dotted and gridded NUCAPS due to fewer footprints with which to calculate cloud cleared radiances Dot NUCAPS overlaid on Gridded NUCAPS Green: good retrieval Yellow: IR retrieval failed but MW-only retrieval successful Red: Both IR and MW failed - Gridded NUCAPS: polar2grid regrids NUCAPS to 10km from ~50km at nadir (~150km at edge of scan). NO INTERPOLATION. All this means is that a single retrieval footprint is now represented by ~25 (~225) identical grid cells. This breaks footprint into smaller parts and gives it a zig-zag edge but the benefits are that (1) it
preserves a realistic footprint size towards edge of scan, and (2) allows a one-to-one comparison with dot NUCAPS product. - Note the mismatch in QC between dotted and gridded product. This is due to the latter being from the CSPP (direct broadcast) data stream which has 7 instead of 9 fields of view (previous slide). Displaying Data & Recommended Fields Can view as cross section or plan view via volume browser Volume Browser NUCAPS-CONUS choose field Misc Gridded NUCAPS choose level load Temp: Temp, Potential Temp, Temp Lapse Rate, Virtual Temperature Moist: Dewpoint, Dewpoint Dep, Mixing Ratio, RH, Theta E, Saturated Theta E, Specific Humidity Stability: Computed CAPE, Most Unstable CAPE, Computed CIN, Lapse Rate (can view on layers via Pres Standard Layers choose layer) Vertical Totals, Total Totals, Showalter Index, K Index, Cross Totals Or use the NUCAPS_AllTilts.xml procedure to display temperature and toggle through all the levels
Forecast Challenge: Diagnosing Pre-Convective Environment The vertical distribution of temperature and moisture in the lower atmosphere determines convective potential Forecasters use a combination of in situ observations, satellite data, and models to determine the location of boundaries and areas of instability Ability to view plan view and cross sections of NUCAPS data in a beta version were demonstrated at the 2016 Hazardous Weather Testbed Experimental Warning Program Sample convective outlook from SPC Sample model analysis Sample model analysis 15 Gridded NUCAPS Convection Application Images from GOES-R HWT Blog
Cold front easily identified in Gridded NUCAPS We recently gained the ability to create cross sections through the NUCAPS swaths. This will be helpful for diagnosing phenomena such as boundaries and convective instability. The first image below is a plan view display of theta-e at 660 mb across the region. Obvious is the much cooler, drier air behind the cold front (low theta-e) with moist, warmer air ahead of it to the east (high theta-e). Also plotted is a line, denoting the location for which the cross-section (image below) was taken, through the cold front. The cross-section depicts theta-e vertically through the atmosphere. This provides another perspective on the cold front, which is obvious in the image. Gridded NUCAPS Convection Application Images from GOES-R HWT Blog We took a look at a NUCAPS plan view image of mid-level moisture (754 mb mixing ratio) from 19Z. Image shown below. Areas of higher moisture were apparent over south-central Missouri in our SGF CWA, and over the St. Louis metro area. Several hours later, we noted that convective activity was focused in these general areas. The few cells that developed over our CWA were over the south-central part of the state. Much more
significant convection triggered over the St. Louis area. JP 9 May 2016 Observed soundings taken at OUN 12/18 UTC NUCAPS Sounding (Red) captured the midlevel dry air signature during 19-20 UTC overpass Convective parameters (red in table) were within ~20 % of model CAPE and observations NUCAPS provided additional Soundings over a large area and between special/synoptic observations Tornado occurred near Moore, OK 2215 UTC 700 mb Dew Point Depression 9 May 2016 Gridded NUCAPS example to evaluate the pre-convective environment in OK and TX where severe weather was
anticipated on this day 8-15 C Mid-level dry air present Total Totals Index Gridded NUCAPS overpass 19-20 UTC indicates Mid-level dry air present Unstable conditions Strong potential for severe weather 700-500 mb Lapse Rate 7-9 C/km Unstable conditions
850 mb Computed CAPE > 55 Strong potential for severe storms 1100-1400 J/kg Unstable conditions Dots can be overlaid on Gridded NUCAPS fields to help decide which skew-T to click on. Improved spatial context. 20 NUCAPS in AWIPS Things to think about... Radiosondes measures moisture through clouds, NUCAPS measures moisture around clouds NUCAPS can retrieve super-saturation (no limit on 100% RH). May see RH values well above 100% in the gridded product which will impact how AWIPS calculates certain parameters such as dew point and stability indices Data below the surface is masked out in the gridded product
NUCAPS resolution is 50 km near the center but closer to 150 km near the swath edge however the product is Gridded to a uniform 12 km grid for AWIPS NUCAPS can resolve only 4-6 layers of water vapor 6-10 layers of temperature but data is output on the 100 layers used by the radiative transfer model. As a result profiles are smooth despite the number of level available There are 58 levels available in AWIPS and some levels were forced to standard levels for consistency with the forecast process and to allow AWIPS to calculate stability indices (1000, 925, 850, 700, 500, 300, 250, 200, 100) Summary NUCAPS Soundings and Gridded NUCAPS can be used to diagnose temperature, moisture, and stability characteristics of the preconvective environment. NUCAPS Soundings provide soundings between routine radiosonde observations Gridded NUCAPS allows the forecaster to view variables on either plan view or cross-sections NUCAPS retrieves atmospheric information around clouds The best quality data is retrieved under clear to partly cloudy conditions Developer questions to Forecaster
Would you be interested to know how vertical resolution (or degree of smoothing) changes from scene-to-scene? Given what youve learned about satellite soundings, is there any diagnostic, thermodynamic or quality control metric that you would like to visualize as a means to aid your real-time problem solving? Would you be interested in MW-Only NUCAPS retrieval? It provides additional measurement and it can possibly be used to fill the IR+MW product gaps Does NUCAPS (IR+MW) provide enough information (e.g., despite data gaps and coarse spatial resolution) to make sense of the pre-convective environment? Other than the thermodynamic parameters (T/q) what other NUCAPS retrieval parameters (trace gases, surface and cloud properties) would you find valuable?
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