Cloud Physical Properties:
Description and examples
- Goal of the Cloud Physical Product product
- Cloud Physical Product algorithm description
- List of inputs for Cloud Physical Product
- Coverage and resolution
- Description of Cloud Physical Product outputs
- Example of Cloud Physical Product visualisation
- Example of Cloud Physical Product, additional products, visualisation
The Goal of the Cloud Physical Properties (cpp) package is to give a more detailed insight into micro-physical conditions of clouds. This means the thermodynamic phase of the cloud particles at the upper part of the cloud and the vertical integrated liquid water path. In addition to these also other cloud micro-physical parameters are retrieved. These additional parameters are made available as they may be of interest to some users. But they are not validated and are not part of the official product.
A central step within the cpp retrieval is an iterative process wherein the convergence of cloud optical thickness and cloud particle size is tested. First pre-calculated Look-Up Tables (lut) for ice-phase are used and if this does not succeed liquid water luts are used. The finally used lut-set leads directly to the cloud phase product. In case of water-clouds, the vertically integrated liquid water content is derived from an analytic relation, using auxiliary data (see below).
pps products as input: Cloud Mask
Satellite data: 0.6 microns, 10.8 microns and (1.6 or 3.7 microns), from avhrr or from viirs.
- Sun and satellite angles
- Surface albedo
- Surface emissivity
- Surface temperature
- Water vapour path
These products are available in full imager resolution and for the whole field of view, provided that all requirements are met. Day light is required for the Cloud Physical Properties product.
There are two official products of Cloud Physical Properties:
- Liquid Water Path, in g/m²
- Cloud Phase, in 4 classes, see below
|Class number||Class name|
|1||Cloud phase: liquid|
|2||Cloud phase: ice|
There are three additonal products of Cloud Physical Properties:
- Ice Water Path, in g/m²
- Cloud Optical Thickness, a dimensionless quantity from 0 an up
- Effective Radius, in µm
cloud free, sea
cloud free, land
cloud phase: liquid
cloud phase: ice
Here an example image of the pps Cloud Physical Properties product over northen Europe is displayed. The data are from a noaa19 overpass (orbit 16826) May 14,2012, 11:25 UTC, as received and processed at smhi, Norrköping, Sweden. The corresponding rgb images using avhrr channel 0.6µm,0.9µm,11µm and 3.7µm,11µm,12µm are shown below for comparison with the Cloud Physical Properties.
The cloud physical properties image shown here has been generated with the nwcsaf/pps software. It displays only part of the information available in the product. Also the hdf-viewer (hdfview) available from ncsa is recommended.