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This document provides relevant information on requirements and gaps for the TCDR AVHRR CLARA v2.0 Cloud Properties product (known as CLARA-A2.1) and its associated ICDR v2.x, and the Cloud-CCI (A)ATSR CC4CL/ORAC v3.0 cloud properties TCDR. It is divided into three parts. Part 1 describes the products the present document refers to. Part 2 provides the target requirements for the products. Part 3 provides a past, present, and future gap analysis for the products and covers both gaps in the data availability and scientific gaps that could be addressed by further research activities (outside C3S).
Executive summary
The products associated with the AVHRR CLARA v2.0 Cloud Properties TCDR are described together with their target requirements. For the four cloud products cloud fractional cover (CFC), cloud top pressure (CTP), liquid water path (LWP) and ice water path (IWP) the mean error requirements are 5 %, 50 hPa, 10 gm-2 and 20 gm-2, respectively. Corresponding stability requirements are 2 % per decade, 20 hPa per decade, 3 gm-2 per decade and 6 gm-2 per decade, respectively.
Key Performance Indices (KPIs) for ICDR products to be produced for the extension of the TCDR have been defined using MODIS Level 3 products as reference observations. The KPI test is based on a binomial test against low (2.5%) and high (97.5%) percentiles of the MODIS-CLARA difference distribution. The low and high percentiles are given in the following table:
Variable | KPI: lower percentile | KPI: higher percentile |
CFC | -0.718 % | 0.576 % |
CTP | -7.036 hPa | 4.353 hPa |
LWP | -0.0021 g/m² | 0.0022 g/m2 |
IWP | -0.0031 g/m² | 0.0021 g/m² |
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Variable | KPI: lower percentile | KPI: higher percentile |
CFC | -0.718 % | 0.576 % |
CTP | -7.036 hPa | 4.353 hPa |
LWP | -0.0021 g/m² | 0.0022 g/m2 |
IWP | -0.0031 g/m² | 0.0021 g/m² |
These percentiles are used to check, by means of a binomial test at 5 % significance level, whether the corresponding ICDR differences are consistent with the TCDR differences or not. Further details on these tests are found in the Report on Updated KPIs' (D11).
2.1.5 Discussion of requirements with respect to GCOS and other requirements
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Table 3-1: Spectral channels of the Advanced Very High Resolution Radiometer (AVHRR). The three different versions of the instrument are described as well as their corresponding satellites. Notice that channel 3A was only used continuously on NOAA-17 and on the Metop satellites. For the other satellites with AVHRR/3 it was used only for shorter periods. (Table taken from reference document D5 but extended with information on satellites Tiros-N and Metop-C).Anchor table3_1 table3_1
Channel Number | Wavelength(micrometers)AVHRR/1 Tiros-N,NOAA-6,8,10 | Wavelength(micrometers)AVHRR/2 NOAA-7,9,11,12,14 | Wavelength(micrometers)AVHRR/3 NOAA-15,16,17,18NOAA-19, Metop-A, Metop-B, Metop-C |
1 | 0.58-0.68 | 0.58-0.68 | 0.58-0.68 |
2 | 0.725-1.10 | 0.725-1.10 | 0.725-1.10 |
3A | - | - | 1.58-1.64 |
3B | 3.55-3.93 | 3.55-3.93 | 3.55-3.93 |
4 | 10.50-11.50 | 10.50-11.50 | 10.50-11.50 |
5 | Channel 4 repeated | 11.50-12.50 | 11.50-12.50 |
Table 3-2: Channel 3A and 3B activity for the AVHRR/3 instruments during daytime. Notice that the given time periods show the availability in the CLARA TCDR v2.0 and not the true lifetime of the individual sensor/satellite. The table is taken from reference document D5 (slightly modified with respect to end of data record).Anchor table3_2 table3_2
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Figure 3-2: Overview of all NOAA satellites (except NOAA-19 launched in 2009) carrying the AVHRR instrument. Notice that the figure only shows expected operational life and not the true operation periods for individual AVHRR instruments. The latter are shown in Figure 3-3. (From https://www.nesdis.noaa.gov/content/noaa-15-makes-100-thousandth-orbit).
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Figure 3-3: Overview of operation times for the AVHRR instrument on individual satellites from NOAA-6 in 1979 until 2018, although not including Metop-C being launched in November 2018. (From https://www.dlr.de/eoc/en/desktopdefault.aspx/tabid-9136/19476_read-45195/)
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