NPOL: GPM Precipitation Science Research Facility
NASA S-Band Dual-Polarimetric Radar (NPOL)
NPOL is NASA's premier weather radar. It is one of only two mobile S-band
dual-polarization radars (the other being NCAR's SPOL). When not being
deployed for PMM/GPM field campaigns, it is operated near NASA's Wallops
Flight Facility in Newark, MD.
NPOL has a wavelength of 10.65 cm, an operating frequency of 2700-2900 MHz,
variable PRF of 500 and 1000 Hz with a 0.95 degree beam width. NPOL can
operate with both horizontal and vertical polarization in both simultaneous
and alternating modes. The radar has a prime-focus parabolic reflector which
is 8.5 m in diameter and is housed on five sea-tainers. When readied for
deployment, the entire radar and antenna system is stored within the five
The image to the right shows a network of rain gauges and disdrometer deployed
in the NPOL domain. All of these instruments are being used to help validate
GPM satellite over an area of 0.5 degrees latitude x 0.5 degrees latitude.
Click on on the image to see a higher resolution map of the network.
Radar imagery on this page was generated using PyART
Helmus, J.J. and Collis, S.M., 2016. The Python ARM Radar Toolkit (Py-ART), a Library forWorking with Weather Radar Data in the Python Programming Language. Journal of Open Research Software, 4(1), p.e25. DOI: http://doi.org/10.5334/jors.119.
Latest NPOL Imagery
Latest NPOL Radar Animations
|Reflectivity [dBZ]||Radial Velocity [m/s]||Differential Reflectivity [dB]
|Corellation||Differential Phase [deg]||Specific Differential Phase [deg/km]
Click thumbnails to view animatewd gif!
Latest Quasi-Vertical Profile
A quasi-vertical profile (QVP) is a conical scan at 20.0 degrees
elevation. The reflectivity, differential reflectivity, correlation,
and differential phase are azimuthally averaged by range bin, and are
presented in a height-versus-time format. A height of 10 km is
approximately 30 km range from NPOL (see figure). Per Ryzhkov et al.
2016, the temporal evolution of microphysical processes that govern
precipitation is a key benefit to this methodology. Through this
technique, NPOL will be monitoring characteristics and behavior of the
melting layer, regions of dendritic growth, riming, and snow aggregation
with high vertical resolution. Comparisons with vertically looking
remote sensors such as the Micro-Rain-Radar (MRR) and the GPM
Dual-Frequency Precipitation Radar (DPR) will be performed for
validation within the atmospheric column.
More QVP info:
Radar Calibration Information
|The pointing accuracy of the NPOL antenna is monitored by
analyzing daily SunCal scans. These plots are generally run twice daily, once in the
morning and the other in later afternoon, which provides additional detail on the
level of the dish.
The plots to the right show the time series of estimated pointing error, as
determined by the SIGMET SolarCal utility for Azimuth (top) and Elevation (bottom).
Click on the image to see an expanded image. The blue triangles represent the
AM scans, while the red triangles represent the PM scans. Ideally, these would
be centered +/- some delta around zero, so an offset indicates a possible
actual pointing issue.
More SunCal info
Absolute Calibration: GPM uses both Self-consistency and comparisons between
disdrometers and the radar to provide estimates of the absolute calibration.
Click here to see the frequently updated NPOL Bias Table.
Use the pull down menu to display a monthly data availability plot similar
to the one to the left of this panel.
Use the pull down menu to display a yearly data availability plot.
NPOL Precipitation Events
Use the pull down menu to display a monthly NPOL precipitation event plot similar
to the one to the left of this panel.
Use the pull down menu to display a yearly NPOL precipitation event plot.
Notes on the Hydrometeor Identfication Images
The HID product is generated using software provided by Colorado State University
and is based on the continued work of
Dolan et al. (2013).
The classifications are: