The
Terra overpass time is around 10:30am (local solar time) in its descending mode
and 10:30pm in ascending mode. The Aqua overpass time is around 1:30pm in
ascending mode and 1:30am in descending mode. (Wan et al., 2004; IJRS)
MODIS Level-3 Hierarchical Data Format (HDF) product files have standardized filenames. The prefix MOD is reserved for files containing data collected from the Terra (AM) platform and MYD is reserved for files containing data collected from the Aqua (PM overpass) platform.
all times are UTC time, not local time nice discription of MOD11C1 Daily CMG LST
NARR: through a better representation of the terrain (heights, vegetation, soil type).
from
https://data.noaa.gov/dataset/ncep-north-american-regional-reanalysis-narr-for-1979-to-present
How are the NARR topography and land/water masks created?
A: The NARR topography and land/water masks are created in the same way as those of the then operational Eta model, following the procedure as follows.
Each model grid box is split into 2 x 2 subboxes, and terrain elevation read off terrain data (USGS 30 s data where available), collecting values and percentages of water that happen to fall within each of the subboxes. Using these, mean subbox elevation and percentage of water is obtained. Subsequently, for each grid box, mean and silhouette elevations are calculated. Silhouette elevation is calculated by looking at each pair of subboxes as seen from two directions perpendicular to sides of the box, amounting to four pairs total, each time taking the higher value, and subsequently averaging these four higher values. Following this, nine-point Laplacian of the mean orography is calculated for every box. Where the Laplacian is positive, mean is used for the box elevation. Where it is negative, silhouette is used (Mesinger, Bull. Amer. Meteor. Soc., 1996, p. 2646-2647).
Subsequently, an effort is made to minimize closing up of significant valleys and mountain passes that may have happened within the silhouette part of the so obtained topography. This is done by looking for points for which in at least in one of the four possible directions the average elevation of three nearest neighbors in that direction, centered on the point considered, is less than both the average elevation of the three nearest points on one side of these three points, and also of the three nearest neighbors on the other side of the three points. If so, irrespective of the sign of the Laplacian, the mean elevation is used for that point. Points are declared water if more than 50 percent of their area is covered by water according to the topography data read.
This is followed by rounding off to reference interface elevation, and elimination of "windless" points created as a result. Land points that have winds at all four of their vertices blocked are raised as needed to reach the lowest unblocked wind. Isolated water points, or water points that have only one of their nearest neighbors water and are at sea level, are also raised to reach the lowest wind, and are declared land. Otherwise, land is removed at one of the water point's four corners, to free one of the blocked winds. The corner chosen for land removal is one that has the smallest three-point averaged elevation.
Elevation of water points above sea level is checked for presence of neighboring water points with a different elevation, and, if so, elevation of all neighboring water points is made equal.
from
http://www.emc.ncep.noaa.gov/mmb/rreanl/faq.html#land-mask