Starting April 2025 NCEP temperature and geopotential height products are now based on the Global Forecast System/Global Data Assimilation System (GFS/GDAS) products for the entire profile. Some overlap with the previous Advanced Microwave Sounding Unit (AMSU) -based data is provided for April to June 2025.
Beginning in June 2025 the NOAA Polar Orbiter Environmental Satellites (NPOES) carrying the last of the AMSU instruments will be retired. >With this retirement, NCEP will be providing its products to NDACC using GFS/GDAS throughout the profile instead of only the lower levels. More information about the datasets is available in the NCEP metadata file at https://www-air.larc.nasa.gov/pub/NDACC/PUBLIC/meta/ncep/.
Unlike the transition from the Stratospheric Sounding Unit (SSU) to AMSU transition in 2001, this transition will provide both datasets to NDACC for a short overlap period in mid-2025. Access to this data at the NDACC Data Host Facility (DHF, https://www-air.larc.nasa.gov/missions/ndacc) is somewhat modified to accommodate the overlap data.
Data can be accessed from the DHF home page links to the directory tree organization of files as seen in Figure 1.
Figure 1: Links to the directory structure files from the NDACC DHF home page.
NCEP extraction tools have been expanded to offer the choice of AMSU or GSF/GDAS to extract data at a single station in the QUERY tools section found on the DHF home page as shown in Figure 2. Note that with the transition to the fully GFS/GDAS-based product the number of stations for which data is provided has increased to 100 which now includes all NDACC currently active stations.
Figure 2: Depiction of the tool to extract time series data at a single site.