[画像:RSMC Tokyo for Nowcasting logo] JMA's RSMC Tokyo for Nowcasting supplies national meteorological services with graphical nowcasting products to help improve capacity for disaster risk reduction.

[画像:Realtime products]On 20 December 2018, JMA began providing graphical products titled Heavy Rainfall Potential (HRP) and High-resolution Cloud Analysis Information (HCAI) via its website as part of its regional center operations.

Heavy Rainfall Potential (HRP)

[画像:Heavy Rainfall Potential] HRP provides information about the possibility of rainfall with an intensity of 20 mm/h or more associated with deep convective clouds. The product is derived from Himawari-8/9 satellite imagery and covers the area of 60°N – 60°S and 80°E – 160°W. It is updated every 10 minutes to support monitoring of rapidly developing convective clouds.

Areas where rainfall is possible or probable are identified by detecting convective clouds that have tops with a low brightness temperature because the tops of such clouds causing heavy rainfall reach higher altitudes or even the tropopause.

The HRP algorithm uses the brightness temperatures of the three Himawari-8 infrared bands (6.2 micrometers (T_6.2), 10.4 micrometers (T_10.4) and 12.4 micrometers (T_12.4)) for detection of deep convective clouds. The concepts outlined below are adopted to detect convective clouds with high tops.

• T_6.2 is lower than T_10.4 and T_12.4 when clouds are in the development stage and their tops do not reach the tropopause.
• T_6.2, T_10.4 and T_12.4 are almost identical when convective cloud tops reach the tropopause.
• T_6.2 may be higher than T_10.4 when cloud tops overshoot into the stratosphere.
• The temperature difference between T_10.4 and T_12.4 increases when thin cirrus clouds are observed.

Threshold values for the detection of deep convective clouds are adjusted to place priority on the improvement of detection probability.

This product helps to clarify the possibility of heavy rainfall. It should be noted that HRP does not provide actual measurements of rainfall or estimations of precipitable water amounts because the imagers on board the Himawari-series satellites used capture infrared radiance from cloud tops but extract few signals relating to internal cloud structures.

For more information, refer to "Users' Guide to Imagery with Heavy Rainfall Potential Areas".

High-resolution Cloud Analysis Information (HCAI)

HCAI provides data on cloud top height, cloud mask, cloud type, dust mask and snow/ice mask. The product is also derived from Himawari-8/9 satellite imagery and covers the area of 60°N – 60°S and 80°E – 160°W. The product is updated on an hourly basis.

The HCAI generation algorithm is largely derived from the cloud product algorithm developed by EUMETSAT/ NWC-SAF (Nowcasting Satellite Application Facility).

[画像:Cloud Top Height] Cloud top height is determined using the H2O-IRW intercept, radiance ratioing or interpolation (in comparison with NWP data) methods. Cloud type information is referenced in selection of the method for the Himawari-8 cloud top height algorithm.

[画像:Cloud Mask] This shows information on clear/cloudy status. The Himawari-8 cloud mask algorithm includes a number of cloud detection tests, most of which involve threshold methods based on radiative transfer calculation using NWP-derived atmospheric profiles.

[画像:Cloud Type] Cloud type information is generated via two-stage analysis. The first stage involves determination of optical or radiative properties (e.g., opaque, semi-transparent or fractional) using the Himawari-8 could type/phase algorithm. The second involves the generation of the HCAI cloud type information to clarify meteorological properties.

[画像:Dust] This indicates the results of aerosol detection based on an ash detection algorithm developed by NOAA/NESDIS for GOES-R/ABI application. This detection is part of the Himawari-8 cloud mask algorithm.

[画像:Snow/Ice] Snow/ice mask areas are detected using data from Himawari cloud products covering the last four days and a snow depth product derived from data collected by microwave sensors on board low-earth-orbiting satellites.

For more information, refer to HCAI specifications and High-resolution Cloud Analysis Information derived from Himawari-8 data.

Operational contact: Contact