Ocean Observation from Haiyang Satellites : 2012 – 2014

During 2012 and 2014, China has two Haiyang (which means ocean in Chinese, referred to as HY) satellites operating normally in space which are HY-1B and HY-2A. HY-1B is an ocean color environment satellite which was launched in April 2007 to observe global ocean color and sea surface temperature, and HY-2A is an ocean dynamic environment satellite which was launched in August 2011 to obtain global marine dynamic environment parameters including sea surface height, significant wave height, ocean wind vectors, etc. Ocean observation data provided by HY-1B and HY-2A have been widely used by both domestic and international users in extensive areas such as ocean environment protection, ocean disaster prevention and reduction, marine environment forecast, ocean resource development and management, ocean investigations and scientific researches, etc.

surface temperature and coastal zone dynamic changing information of all Chinese seas.The remote sensing payloads onboard both HY-1A and HY-1B are Chinese Ocean Color and Temperature Scanner (COCTS) and Coastal Zone Imager (CZI).HY-1A is an experimental satellite with a design life of 2 years, and it stopped working in April 2004.HY-1B, which was launched on April 11, 2007, is the successor of HY-1A with several improvements such as increased swath of COCTS, extended design life of 3 years, larger storage capacity, higher transmission rates, etc.As of January 2014, HY-1B has been operating normally for 6 years and 9 months which makes a new record of Chinese low Earth orbit small satellites with the longest effective working life.
HY-2 satellite series is ocean dynamic environment satellites which are designed to obtain ocean surface wind vectors, sea surface height, significant wave height and sea surface temperature of global oceans.HY-2A, which was launched on August 16, 2011, carries four microwave payloads and is capable of observing oceans in all-weather all-time conditions.The four payloads are Microwave Scatterometer (MS), Radar Altimeter (RA), Scanning Microwave Radiometer (SMR) and Calibration Microwave Radiometer (CMR).As of August 2014, HY-2A has been operating normally for nearly 3 years.

Data Acquisition and Distribution
National Satellite Ocean Application Service (NSOAS), which is a commonweal institution under SOA, is responsible for receiving, processing, archiving, managing and distributing all collected data and products of HY satellites.NSOAS owns four ground stations which are located at Beijing, Mudanjiang, Sanya and Hangzhou respectively.

Ocean Color and Sea Surface Temperature
HY-1B/COCTS provides daily, monthly and seasonal averaged ocean color products of chlorophyll-a concentration, suspended materials, yellow substance, etc.The region for regular ocean color products is presented in Figure 1 where the monthly averaged chlorophyll-a concentration product of July 2013 is shown.Regional ocean color products of global oceans are also provided occasionally depending on the actual data acquisition program of HY-1B/COCTS.
Based on the data of HY-1B/COCTS and HY-2A/ SMR, NSOAS provides daily, weekly and monthly Sea Surface Temperature (SST) fusion products of both Northwestern Pacific and global oceans.The monthly SST fusion product of November 2013 is given in Figure 2 to show the form and region of Northwestern Pacific products.HY-2A/SMR is capable of observing SST of more than 90% global oceans every data, the product of January 22, 2014 is shown in Figure 3 for illustration.NSOAS provides global ocean SST fusion products based on HY-2A/SMR and other available SST data sources.A fusion product of December 3, 2013 is shown in Figure 4. NSOAS also provides daily OWV fusion products based on HY-2A/MS data and other available data sources.The OWV fusion products, with the time resolution of 6 h and the space resolution of 0.25°, better satisfies the Nowadays, SSH data fusion of all available RD sources is the only practical approach to obtain more complete global SSH products of each data.NSOAS provides HY-2A/RD meshing products, and one example is shown in Figure 7. HY-2A/RD meshing products are fused with other available RD data sources to provide more delicate and frequently observed SSH products, which are mainly provided to ocean forecast users.

Product Distribution
HY satellite products are distributed to both domestic and international users via internet, dedicated communication systems and manual services, etc.As shown in Figure 8

Application Achievements
As a rapidly developing high technology, HY satellites now play a more and more important role in both ocean economy development and national defense construction of China.HY satellite products are widely used in extensive domains, such as ocean environment protection, ocean disaster management (including prevention, mitigation, warning, response, recovery and assessment), marine environment forecast, ocean resource development and management, ocean right protection and law enforcement, ocean investigations and scientific researches, etc.Some typical application achievements of both HY-1B and HY-2A, which were made in 2012 and 2013, are presented as follows.

Tropical Cyclones
Nowadays, there are only two space-born data sources for global ocean vector wind observation which are HY-2A/MS and the Advanced Scatterometer (ASCAT) carried on Metop satellites of Europe.The major advantage of HY-2A/MS is that its swath, which is about 1500 km, is much wider than that of Metop/ASCAT.A comparison example is shown in Figure 9 which is the observation of typhoon No.15 "Bolaven" in 2012 carried out by HY-2A/MS and Metop/ASCAT, respectively.From Figure 9, it is easy to find that the much wider swath makes the observing data of HY-2A/MS containing more complete information of the "Bolaven" typhoon.With the much wider swath, HY-2/MS is capable of covering more than 90% global oceans every day.All 25 typhoons in 2012 and all 31 typhoons in 2013 were observed by HY-2/MS.Continuous monitoring results of the No.14 typhoon "Libra" in 2012 are shown in Figure 10 for illustration.From HY-2/MS data, we are able to clearly observe the position, strength, extent and structure of a tropical cyclone.Moreover, HY-2A/RD also provides the SSH and SWH data of tropical cyclone areas.All the information is very supportive for tropical cyclone track forecast, storm surge forecast, ocean navigation, typhoon disaster prevention and mitigation, typhoon scientific researches, etc.  ice disaster reduction and emergency response.

Enteromorpha
Enteromorpha is a seasonal large-area ocean disaster which adversely impact local marine environment and economy.In 2013, HY-1B was applied to operational enteromorpha surveillance form May 2 to August 31, and 102 regular reports were distributed by NSOAS.An enteromorpha image obtained by HY-1B/COCTS on June 29, 2013 is shown in Figure 12.The corresponding thematic map is in the lower right of Figure 12 which shows the distribution extent, coverage area, and other necessary information.

Red Tides
Red Tides, which are harmful algal blooms, usually occur in East China Sea.The Second Institute of Oceanography and the East China Sea Environment Monitoring Center provide the operational red tide detection and monitoring based on HY-1B and other satellite ocean color sources.From May to September in 2013, fifty four reports were released to the public via internet.The July 2013 red tide distribution thematic map is shown Figure 13.

Marine Environment Forecast
Marine environment forecast organizations, such as National Marine Environment Forecast Center (NMEFC) and forecast departments of local governments, are the major part of HY satellites users.The data of SST,

Fishery Forecast
Based on the chlorophyll, SST, and SSH data derived by HY-1B and HY-2A, NSOAS has developed fishery forecast models and constructed an operational ocean fishery information forecast system.Fishery forecasts are weekly provided to 9 fishing companies for more than 11 fisheries which are located separately in Pacific, Atlantic and Indian Ocean.Fishery forecast information has effectively increased the fishing production.One fishery forecast example is shown in Figure 15.

Future Plans
China has formulated and implemented several mediumand long-term national plans on the development of HY satellites.HY satellites will be developed in three series, i.e., ocean color environment satellites (HY-1), marine dynamic environment satellites (HY-2), and maritime surveillance and monitoring satellites (HY-3).Besides traditional optical and microwave sensors that have been carried on HY-1A/B and HY-2A, several new type sensors have also been researched and decided to be involved in future HY satellite missions in order to further improve the data accuracy and resolution.
HY-2A observes marine dynamic environment parameters every data including Sea Surface Height (SSH), Significant Wave Height (SWH), Ocean Wind vectors (OWV), Sea Surface Temperature, Water Vapor Content, etc.The SSH, SWH and OWV products observed by HY-2A on January 22, 2014 are presented in Figure 5 to show their own specific forms.

Fig. 1
Fig.1 The monthly averaged chlorophyll-a concentration product of July 2013 derived by HY-1B/COCTS (© NSOAS/SOA, 2013 -All Rights Reserved) , NSOAS distributed products of HY-1B and HY-2A 26.72 TB and 5.79 TB respectively in 2012; products of HY-1B and HY-2A 27.56 TB and 20.93 TB respectively in 2013.From Figure 8, we can clearly find that the distributed data volume of HY-2A products sharply increased from 5.79 TB in 2012 to 20.93 TB in 2013, which illustrates a significant growth on the application of HY-2A.Domestic users of HY satellites include government departments, forecast organizations, research institutions, companies, universities, etc.International users of HY satellites include European Organization for the Exploitation of Meteorological Satellites (EUMETSAT), National Oceanic and Atmospheric Administration (NOAA) of United States, Centre National d'Etudes Spatiales (CNES) of France, Australian Bureau of Meteorology, etc.

Fig. 11
Fig.11 The sea ice remote sensing image obtained by HY-1B on February 8, 2013 and the corresponding sea ice extent thematic map (© NSOAS/SOA, 2013 -All Rights Reserved)

Fig. 13
Fig.13 The red tide distribution thematic map of July 2013 derived with HY-1B/COCTS and other satellite sources

Fig. 14 A
Fig.14 A Northwestern Pacific SST product example which is released to users by the CCTV-13 TV channel

Fig. 15
Fig.15 The September 13, 2013 forecast of Northern Pacific squid fishery including the SST and current information

Fig. 16 AFig. 17
Fig.16 A thematic map of the ice condition around Snow Dragon in the reports provided by NSOAS.(© NSOAS/SOA, 2013 -All Rights Reserved) Fig.17 A remote sensing image of sea ice around Snow Dragon provided by NSOAS