EO Products / Wind Speed and Direction Monitoring
RADARSAT-1 SAR wind speed image near Kodiak Island, Alaska. The intensified gaps flows, reaching over 20 m s-1 or 40 knots, are responsible for williways.
Source: https://www.sarusersmanual.com/ManualPDF/NOAASARManual_CH13_pg305-320.pdf
Product Description
Two types of microwave instruments measure ocean surface winds, the passive microwave radiometer and the active microwave scatterometer (Remote Sensing Systems, n.d.) :
- Radiometer measures ocean surface roughness, which correlates to wind speeds at 10 meters above the water's surface. Radiometers can only retrieve wind speeds, except for the polarimetric radiometer WindSat, that can measure both wind speed and wind direction.
- Scatterometer sends a signal to the Earth's surface, which reflects off the ocean Bragg waves (these are wind generated surface ripples—capillary waves) on the surface of the larger scale ocean waves. The reflected energy measured by the scatterometer is translated using a geophysical model function into a 10 meter neutral wind speed and direction. Scatterometers typically operate at either C-band (~5GHz frequency) or Ku-band (~14 GHz frequency). With special processing techniques, it can only be obtained wind speeds and directions every 12 km over the oceans. Scatterometers can also be used to measure sea ice and land ice characteristics. The scatterometers that have been in operation longer than a brief period are ERS-2 (C-band), QuikScat (Ku-band), and ASCAT (C-band) and scientists are working on merging these long-term wind vectors into a product for climate study. e.g., the ccmp product (Remote Sensing Systems, n.d.). In 2003, both a radiometer (AMSR) and scatterometer (SeaWinds) were flown on the Midori-2 satellite.
Wind speeds from these two instruments showed excellent agreement in rain-free conditions. Sensors, that operate at microwave frequencies, can make measurements day and night and under nearly all-weather conditions. Examples of datasets include:
- 1-DEGREE, MONTHLY Wind Speed
The dataset consists of merged wind speed measurements from the many radiometers in operation since 1987, including SSM/I, SSMIS, and WindSat. These data were all processed in a consistent manner using radiative transfer model and careful instrument intercalibration. The wind speeds from these instruments are used to create a Mean Wind Speed product that is best for use in climatological study (long term time series analysis) (Kent et al., 2013).
- CCMP 4x-Daily VAM Analysis Wind Fields
The Cross-Calibrated Multi-Platform (CCMP) gridded surface vector winds are produced using RSS V7 radiometer winds, QuikSCAT and ASCAT scattereometer winds, quality-checked moored buoy winds, and the ECWMF ERA-Interim Reanalysis model wind field as a background wind (Remote Sensing Systems, n.d.). A 4-dimensional variational analysis (VAM) is used to produce the fully populated nearly-global wind fields from the input data. As such, the CCMP is considered to be a Level-3 ocean vector wind analysis product consisting of four maps daily of a 0.25 degree gridded vector wind field. This product is an update and extension of the original V1.1 CCMP product. RSS has transitioned the CCMP processing code to run using our most up-to-date satellite data observations. All methodology remains the same as that used in the original CCMP product and most of the CCMP processing code is unchanged, with only minor alterations to compensate for the different operating systems and compilers.
- Individual Radiometer and Scatterometer Gridded Binary Data Files
In addition, wind speed is one of the measurements in the radiometer binary gridded data files and is also available along with wind direction in the scatterometer data files. For detailed product information and data access, see the section Satellites.
Product Specifications
BUSINESS PROCESS | SC, SCE, IN, SO, ELD |
DESCRIPTION | Wind and current velocity components (u, v) forming a line or wall of broken ice forced by pressure. Wind speed referred as how fast the air is moving past a certain point. Wind direction referred as a direction occurring during the indicated hour, using 36 points of a compass. |
EO INFORMATION OF INTEREST | Wind speed derived using a variety of channels and separate algorithms to obtain winds in all weather conditions. Wind direction is the oceanographic-convention wind direction, relative to north. The most common reference height for near-surface ocean wind measurements is 10 meters above sea level. Active and passive satellite remote sensing provide high-resolution, near-surface ocean wind measurements over the ice-free ocean multiple times per day. |
MAIN PROCESS STEPS | The radiometers measure ocean surface roughness, which can be correlated to wind speeds at 10 meters above the water's surface. Scatterometers measure the radar cross section of the ocean surface and a Geophysical Model Function (GMF) provides the radar cross section, as a function of the equivalent neutral wind vector at 10 m, incidence angle, relative azimuth angle, radar frequency, and polarization. Scatterometer allows to measure both speed and wind direction. |
INPUT DATA SOURCE | Microwave radiometers for wind speed: SSMI/I and SSMIS (1987-present), TMI (1997-2015), AMSR-2 (2012-present), AMSR-E (2002-2011), GMI (2014-present), SMAP (2015-present). Polarimetric scatterometers for wind speed and direction: windSat (2003 – present), QuikScat (1999-2009), SeaWinds (2003 (apr-Oct), ASCAT (Metop A and B) (2007-present) Assimilation of Sea Ice Concentration and/or Thickness |
SPATIAL RESOLUTION AND COVERAGE | Global Ocean, Spatial resolution 1km, 12 km to 111 km |
ACCURACY / CONSTRAINS | Wind direction: 0. to 360.0 deg Wind speed: Valid range from 0 to 50 m/s |
LIMITATIONS | Wind speed; less detection in the higher wind range (> 60 kt), near the coast, sensitive to rain,sun glint, rain, RFI, near sea ice or land (~50 km no rain, ~75 km in rain). A daily gridded map is not strictly comparable to the daily average output from a numerical model. The interpretation of data can indeed be challenging, especially when handled by personnel without extensive experience in the field. |
TEMPORAL RESOLUTION | 6 hours, daily, monthly Products available from 1 Jan 2016 to 8 Oct 2023 1987 - present |
FREQUENCY UPDATE | Daily – 12:00 UTC at day + 1; daily at 0:00 UTC at day + 2 |
DELIVERY / OUTPUT FORMAT | NetCDF-3, NetCDF-4 |
ACCESSIBILITY | Copernicus Marine Service |
Business Process Challenges
Ship Construction (SC) Challenges
- SC-1 Lifting Operations
- SC-2 Tow Operations
- SC-6 Finding Suitable Ice During Sea Trials
- SC-7 Ship Operation in Ice During Sea Trials
Ship Certification (SCE) Challenges
Insurance (IN) Challenges
Ship Operation (SO) Challenges
- SO-3 Navigating Along (or just inside) the Ice Edge
- SO-4 Avoiding Ship Icing Conditions
- SO-6 Oil Spill Monitoring
- SO-10 Search & Rescue Operations
This page has no comments.