Contents:

Algorithm Description
Scientific Data Sets
Local Attributes
Global Attributes
Quality Assurance

MOD11C1 Daily CMG LST

This daily global LST product provides temperature and emissivity values at 0.05 degree latitude/longitude climate model grids (CMG). The exact areal size of the equal angle grids varies with latitude, and it is 5.6km by 5.6km at the Equator.

Algorithm Description

The temperature and emissivity values in MOD11C1 are derived by reprojection and average of the values in the daily MODIS LST/E product (MOD11B1) at 5km equal area grids in the sinusoidal projection. Before making reprojection in the production of MOD11C1, cloud-contaminated daytime and nighttime LSTs are removed by the double-screen scheme, which is described in the LST validation paper (Wan et al., 2002). In the first step, the temperature difference distributions between the LSTs at 5km grids retrieved by the day/night LST algorithm and the LST values aggregated to 5km grids from those retrieved by the generalized split-window algorithm are calculated for all grids in northern or southern hemisphere, for daytime and nighttime LSTs, respectively. The LSTs which correspond to the 1% of the difference distributions by the upper and lower ends are removed. In the second step, the histogram of difference between daytime and nighttime LSTs is used to remove the grids contaminated with cloud effects after the first screen described above: screen off 0.5% of the daytime and nighttime LST pairs by the upper and lower ends of the LST difference distribution. The retrieved emissivity values corresponding to these removed LSTs are also removed. After cloud-contaminated daytime and nighttime LSTs are removed, the LST values aggregated to 5km grids from those retrieved by the generalized split-window algorithm are used to supplement the LSTs retrieved by the day/night LST algorithm at grids where there is no valid pair of day and night observations (usually in high-latitude regions). Due to this LST supplement, the spatial coverages of LSTs are larger than the spatial coverage of retrieved emissivities in the MOD11C products.

Scientific Data Sets (SDS)

There are 15 SDSs in the MOD11C1 product as shown in Table 16. 

Table 16. The SDSs in the MOD11C1 product.
 
SDS
Name		 Long
Name		 Number
Type		 Unit Valid
Range		 Fill
Value		 scale
factor		 add
offset
LST_Day_CMG Daily daytime 3min CMG
Land-surface Temperature		 uint16 K 7500-65535 0 0.02 0.0
QC_Day Quality control for daytime
LST and emissivity		 uint8 none 0-255 0 NA NA
Day_view_time Time of daytime Land-surface
Temperature observation (UTC)		 uint8 hrs 0-120 0 0.2 0
Day_view_angle View zenith angle of
daytime
Land-surface Temperature		 uint8 deg 0-130 255 1.0 -65.0
LST_Night_CMG Daily nighttime 3min CMG
Land-surface Temperature		 uint16 K 7500-65535 0 0.02 0.0
QC_Night Quality control for nighttime
LST and emissivity		 uint8 none 0-255 0 NA NA
Night_view_time Time of nighttime Land-surface
Temperature observation (UTC)		 uint8 hrs 0-120 0 0.2 0
Night_view_angle View zenith angle of nighttime
Land-surface Temperature		 uint8 deg 0-130 255 1.0 -65.0
Emis_20 Band 20 emissivity uint8 none 1-255 0 0.002 0.49
Emis_22 Band 22 emissivity uint8 none 1-255 0 0.002 0.49
Emis_23 Band 23 emissivity uint8 none 1-255 0 0.002 0.49
Emis_29 Band 29 emissivity uint8 none 1-255 0 0.002 0.49
Emis_31 Band 31 emissivity uint8 none 1-255 0 0.002 0.49
Emis_32 Band 32 emissivity uint8 none 1-255 0 0.002 0.49
QC_Emis * Quality control for retrieved emissivities uint8 none 0-255 0 na na

Note *: bits 03-00, nighttime view angle flag, for the index of nighttime view angle sub-range; and bits 07-04, daytime view angle flag, for the index of daytime view angle sub-range.

Local Attributes

The local attributes for SDSs LST_Day_CMG and LST_Night_CMG are similar to those in Table 4. 

Global Attributes

Three ECS global attributes and 16 product-specific global attributes are stored as metadata. The ECS global attributes, CoreMetadata.0, ArchiveMetadata.0 and StructMetadata.0 are stored as very long character strings in PVL format. 

CoreMetadata.0 contains information about the product during production and is used to populate the EOSDIS data base for user support. They are similar to those of MOD11A1.

Quality Assurance

The bit flags in the QC SDS are listed in Table 17 .

Table 17. Bit flags defined in the QC SDS in the MOD11C1 product.  Note that bit 0 is the least significant bit. 
 
bits Long Name Key
1 & 0 Mandatory QA flags 00=LST produced, good quality, not necessary
   to examine more detailed QA
01=LST produced, other quality quality,
   recommend examination of more detailed QA
10=LST not produced due to cloud effects
11=LST not produced primarily due to reasons other than    cloud
3 & 2 Data quality flag 00=good data quality
01=other data quality pixel
10=LST affected by nearby clouds and/or sub-grid
  clouds and/or ocean
11=LST screened off
5 & 4 Emis Error flag 00=average emissivity error <= 0.01
01=average emissivity error <= 0.02
10=average emissivity error <= 0.04
11=average emissivity error > 0.04
7 & 6 LST Error flag 00=average LST error <= 1K
01=average LST error <= 2K
10=average LST error <= 3K
11=average LST error > 3K