NextGen
Introduction:
NextGen products are designed for Federal Aviation Administration use. This contains standard products as well as several additional products (e.g., radial velocity shear).
Composite reflectivity derived from Mosaic3D
Products:
- CREF- 30 min Forecast
Composite Reflectivity -30 min Forecast
This composite reflectivity has been edited with a neural network quality controled algorithm (QCNN; Lakshmanan 2007). The unit of this field is dBZ. This is a 30 minute forecast for this product.
Lakshmanan, V., A. Fritz, T. Smith, K. Hondl, G. J. Stumpf, 2007: An automated technique to quality control radar reflectivity data. J. Appl. Meteor., 46, 288-305. - VIL- 30 min Forecast
Vertically Integrated Liquid - 30 min Forecast
The Vertically Integrated Liquid product is derived based on the procedures described in Greene and Clarke (1972). This is a 30 minute forecast for this product.
Greene, D. R. and R. A. Clark, 1972: Vertically Integrated Liquid Water-A New Analysis Tool. Mon. Wea. Rev., 100, 548-552. - Azimuth Shear (0-2 km AGL)
Azimuth Shear (0-2 km AGL)
Difference between Doppler velocities from 0 to 2 km.
- Az Shear (0-2 km) -30 min Max
Az Shear (0-2 km) -30 min Max
The 30 minute maximum Doppler velocity from 0 to 2 km.
- Azimuth Shear (3-6 km AGL)
Azimuth Shear (3-6 km AGL)
Difference between Doppler velocities from 3 to 6 km.
- Az Shear (3-6 km) -30 min Max
Az Shear (3-6 km) -30 min Max
The 30 minute maximum Doppler velocity from 3 to 6 km.
- Severe Hail Index
Severe Hail Index
Indicates severity of hail according to Witt, A., M. D. Eilts, G. J. Stumpf, J. T. Johnson, E. D. Mitchell, K. W. Thomas, 1998: An Enhanced Hail Detection Algorithm for the WSR-88D. Wea. Forecasting, 13, 286–303.).
- Prob of Severe Hail
Prob of Severe Hail
Probability of severe hail according to Witt, A., M. D. Eilts, G. J. Stumpf, J. T. Johnson, E. D. Mitchell, K. W. Thomas, 1998: An Enhanced Hail Detection Algorithm for the WSR-88D. Wea. Forecasting, 13, 286–303.).
- Max Exp Hail Size
Max Exp Hail Size
Maximum expected hail size according to Witt, A., M. D. Eilts, G. J. Stumpf, J. T. Johnson, E. D. Mitchell, K. W. Thomas, 1998: An Enhanced Hail Detection Algorithm for the WSR-88D. Wea. Forecasting, 13, 286–303.).
- Surface Precip Type
Surface Precip Type
The precipitation flag indicates the surface precipitation type and the radar observation representativeness at each grid point. The representativeness of radar observations with respect to surface precipitation estimation is highly correlated to the height of the radar observation and its proximity to the bright band layer (BBL) and to the surface. The top and bottom heights of the BBL are identified from the vertical profile of reflectivity (if it exists) at each radar site, and then objectively analyzed onto the MRMS grid using the RAP 0C height as the background.
Currently, each grid column in the 3-D mosaic grid is analyzed and classified.
- -1: no radar coverage
- 0: no precipitation
- 1: surface precipitation is stratiform rain, and radar observation is below the bottom of the BBL
- 2: surface precipitation is stratiform rain, and radar observation is inside or above the BBL
- 3: surface precipitation is stratiform snow, and radar observation is below 1 km AGL
- 4: surface precipitation is stratiform snow, and radar observation is above 1 km AGL
- 5: mixed phase precipitation (place holder, not currently used)
- 6: convective precipitation
- 7: convective precipitation with potential hail contamination
- 8: orographically enhanced precipitation (place holder, not currently used)
- 9: tropical (warm cloud microphysics) precipitation
A grid column is classified as being convective if one of the following criteria is satisfied:
- the reflectivity at any height outside bright band (if one exists) is greater than 50 dBZ, or
- if the reflectivity at -10°C height or above is greater than 30 dBZ, or
- if there is one or more lightning flashes in the bin location.
Using a VPR to determine if a grid column is tropical (reference Xu et al., 2007, .doc, 1.2 MB):
- Using an hour-average VPR and the 0C level from the RAP, a VPR is searched downward from either the bottom of the brightband (as identified from the radar BB algorithm) or the 0C level.
- A VPR that is nearly vertical or increases monotonically below the freezing level is assumed to be tropical (Houze, 1993). All grid points within that radar umbrella with echo > 30 dBZ are then designated as tropical and the tropical Z-R is used.
- Since storms may extend away from the radar umbrella into another radar's domain that does not have enough data to compute a VPR, an algorithm assigns the tropical Z-R to echoes > 30 dBZ that are adjacent to the original tropical echo.
Temperature soundings are obtained from the RAP 20 km model analysis.
- Surface Precip Phase
Surface Precip Phase
The 2-D surface precipitation phase indicates the precipitation state (frozen or liquid) at each grid cell.
- Height-Freezing Level
Height-Freezing Level
Height of the 0C isotherm from the RAP model.
- Bright Band Top
Bright Band Top
2-D analysis of bright band top heights derived from single radar vertical profiles of reflectivity
- Bright Band Bottom
Bright Band Bottom
2-D analysis of bright band bottom heights derived from single radar vertical profiles of reflectivity
- Radar Quality Index
Radar Quality Index
The Radar Quality Index is an indicator of radar quality with respect to beam height and the 0C height. Data closest to the radar (ground) and below the 0C height have the highest quality, i.e., values close to 1. Data at far ranges and above 0C have the lowest values.
Zhang, J., Y. Qi, C. Langston, B. Kaney, 2011: Radar Quality Index (RQI) - a combined measure for beam blockage and VRR effects in a national network. Weather Radar and Hydrology
- Composite Reflectivity
Composite Reflectivity
This cref has been edited with a neural network quality controled algorithm (QCNN; Lakshmanan 2007). The unit of this field is dBZ.
Lakshmanan, V., A. Fritz, T. Smith, K. Hondl, G. J. Stumpf, 2007: An automated technique to quality control radar reflectivity data. J. Appl. Meteor., 46, 288-305. - Height CREF (MSL)
Height CREF (MSL)
This variable is the height of the grid level where the column maximum reflectivity (composite reflectivity) is found. The unit is km above MSL.
- CREF - Non QC'ed
CREF - Non QC'ed
The composite reflectivity is the maximum reflectivity in each grid column in the 3-D mosaic. This cref has not been quality control edited to remove non-precipitating echoes. The unit of this field is dBZ.
- Vertically Integrated Liquid (VIL)
Vertically Integrated Liquid (VIL)
The Vertically Integrated Liquid product is derived based on the procedures described in Greene and Clarke (1972).
Greene, D. R. and R. A. Clark, 1972: Vertically Integrated Liquid Water-A New Analysis Tool. Mon. Wea. Rev., 100, 548-552. - VIL Density
VIL Density
The Vertically Integrated Liquid Density product is derived based on the procedures described in Amburn and Wolf (1997).
Amburn, S. A. and P. L.Wolf, 1997: VIL Density as a Hail Indicator. Wea. Forecasting, 12, 473-478.. - Echo Top (18 dBZ)
Echo Top (18 dBZ)
The echo top height is obtained by searching each grid column in the 3D reflectivity mosaic grid, from top to bottom, until the first reflectivity value greater than 18 dBZ is found. The height of the grid level where the reflectivity value was found is recorded as the ETP18 value for the given grid cell. The unit of the echo top is km above MSL.
- Hybrid Scan Refl (HSR)
Hybrid Scan Refl
The hybrid scan reflectivity is a 2-D mosaic of single radar hybrid scan reflectivity fields. The single radar hybrid scan reflectivity is obtained by searching each grid column in the single radar 3D reflectivity Cartesian grid, from bottom to top, until the first non-missing reflectivity value is identified. The reflectivity value is then recorded as the single radar hybrid scan reflectivity (in dBZ) at the given grid cell, and the height of the grid cell is recorded as the single radar hybrid scan height.
- Seamless HSR -VPR Corr
Seamless HSR -VPR Corr
The Seamless Hybrid Scan Reflectivity at any range/azimuth bin with partial blockages of 10 to 50% is a weighted mean of reflectivities from the PPS-type hybrid scan and from the next tilt above. See here.
The VPR correction uses and average VPR and adjusts the radar data form aloft to the surface. See Zhang, J., Y. Qi, 2010: A Real-Time Algorithm for the Correction of Brightband Effects in Radar-Derived QPE. J. Hydrometeor, 11, 1157–1171. - Height HSR (AGL)
Height HSR (AGL)
This field is the height of the lowest non-missing single radar hybrid scan reflectivities at each MRMS grid cell. The unit of Height Hybrid Scan Reflectivity is meters AGL (above ground level).