Argo data quality control based on climatological convex hulls

This report discusses a new method of identifying erroneous data in temperature and salinity (T/S) profiles measured by Argo profiling floats. The proposed method uses World Ocean Atlas 2009 (WOA09) climatology to classify good against bad data. An 'n' sided polygon (convex hull) with least area encompassing all the points is constructed based on the Jarvis March algorithm. The mean and standard deviation fields of temperature and salinity obtained from WOA09 corresponding to each standard depth are used for building these polygons. Subsequently Points In Polygon (PIP) principle which is implemented using ray casting algorithm is used to classify the T/S data as within or without acceptable bounds. It is observed that various types of anomalies in the Argo profile data viz., spikes, bias, sensor drifts etc can be identified using this method

Marine Meteorological Atlas of Tropical Indian Ocean

This report discusses the preparation of climatology from the data which is from the ship observations obtained from the Indian Meteorological Department (IMD) and Naval Operations Data Processing and Analysis Centre (NODPAC). Processing of these datasets, extraction of surface meteorological variables and SST (Sea surface temperature), the quality control (QC) procedures followed are discussed. The individual records of International Comprehensive Ocean-Atmosphere Dataset (ICOADS) and those obtained from IMD are compared and the unique records from IMD data are extracted. The enhancement in ICOADS climatology after adding the unique records from IMD data and NODPAC is checked. ICOADS dataset has been found to be self robust, as there is no much significant improvement in the climatology even after adding new records . Frequency distribution of the ICOADS dataset alone and after adding new records showed no much difference. Spatial correlation between ICOADS monthly climatology fields before and after adding the new records, is greater than 0.9 at all grid point

MaMeAT - A tool for visualizing marine meteorological data for Naval applications

This report discusses various functionalities of tool developed for use by Naval Operations Data Processing and Analysis Centre (NODPAC) a wing of Indian Navy. The data for this tool is obtained from the Indian Meteorological Department (IMD), Naval Operations Data Processing and Analysis Centre (NODPAC) and individual records of International Comprehensive Ocean-Atmosphere Dataset (ICOADS). These data sets are processed, quality controlled and merged to form a unique data set for enhancing the marine met climatology of Indian Ocean. The IMD and NODPAC data are compared with the unique records from COADS and duplicates are eliminated. With addition of around 12% unique records to ICOADS data, enhanced climatology is regenerated. With this base data, Graphic User Interface (GUI) based tool is build for visualizing parameters viz., SST, SLP, Wind, Relative Humidity, SSS and bathymetry. This tool has capability to generate climatology dynamically between any chosen periods apart from visualizing various plots which are useful for Navy while at sea. Also provision for adding newly observed marine met data is provided making this most robust tool for use by the Indian Navy

INCOIS-Real time Automatic Weather Station(IRAWS) dataset - Quality control and significance of height correction

The INCOIS-Real time Automatic Weather Station(IRAWS) program was started in the year 2009 and was first installed onboard ORV Sagar Nidhi. Currently, there are 36 ships carrying IRAWS setup. Apart from storing one minute observations in the log onboard the ship, hourly averaged observations are reported through INSAT satellite communication. This report briefs about the hourly dataset of IRAWS and its quality control. In this report, QC results of SST and all meteorological parameters except radiation parameters is discussed. Specific quality check was applied to wind speed (WS) and sea surface temperature (SST) observations. The WS observations measured onboard few ships had a dimensional correction and SST was observed only on few ships. As SST observations are required to compute meteorological variables like DBT, RH, WS to standard height of 10 m, level-3 dataset of AVHRR SST was utilized in place of IRAWS SST wherever the data is found to be faulty. On similar terms bias correction could not be applied to IRAWS SST with the help of AVHRR SST as the error in SST observations are due to the failure of sensor. However all those IRAWS SST observations that passed the QC check were observed to be of high quality and have a correlation coefficient of 0.5 with AVHRR SST and is significant at 95% significant level. Apart from SST and radiation observations, all other parameters observations are found out to be of good quality with 70 to 90 QC pass percentage . Apart from the details of QC check, significance of representing climate variable at a homogeneous standard height is also shown in this repor

A Roadmap for Unified Ocean Modeling and Forecasting system for INCOIS

INCOIS, being the nodal organization to provide operational oceanographic services, is actively involved in the numerical modeling of ocean circulation, waves, tsunami and storm-surge as well as regional coupled ocean-atmosphere models for the prediction of track and intensity of tropical cyclones. In order to optimise the models used in INCOIS for these activities and to make a seamless prediction system from global to regional domains, it was decided to have a revisit on the ocean modeling efforts of INCOIS. Outcome of this review as well as a proposal to develop a seamless prediction system is documented in this report. It is envisaged that this document will be used as a guideline for the future ocean modeling efforts in INCOI

Human centrifuge controller

In April 1985, Systems Engineering Division (SED), NAL was13; entrusted by Indian Air Force (IAF) with the task of upgrading and rebuilding the aging electronic control desk for the Human Centrifuge System (HCS) at the Institute of Aviation Medicine (LAM), Bangalore. This report outlines HCS existing at IAM, its working and use. The NAL designed, personal computer (PC) based electronic control desk used with the HCS to control the rotational speed of the Human Centrifuge (HC) is described. The control desk is used for running the HC to produce various (acceleration) patterns such as normal g profiles and combat g profiles which are generally experienced by pilots. The PC is used for speed reference signal generation, supervision of the sequence of operations to be carried out at the start of the centrifuge and continuous checking of the correct operation of the overall HCS.13; The NAL designed control desk functionally replaces the original control desk and all the safety features that existed earlier have been retained in the new controller. Use of PC has resulted in a flexible programmig environment and use of the latest available solid state components employed in building the controller has resulted in a reliable system

Spatio-temporal evolution of chlorophyll-a in the Bay of Bengal: a remote sensing and bio-argo perspective

Argo floats equipped with sensors to measure Dissolved Oxygen, Chlorophyll-a and backscattering are deployed in the Arabian Sea, Bay of Bengal and Southern Indian Ocean as part of Indian Argo program. In this study, abnormal chlorophyll-a bloom observed by a float with WMO ID 2902086 deployed in the south central Bay of Bengal is analyzed. High concentration of chlorophyll > 0.8 mg/l is observed during December 2013. This period is also associated with drop in temperature and increase in salinity. Analysis of data from the bio-Argo float has shown the impact of many cyclones and depressions that occurred during the period. Of particular importance is cyclone ‘Madi’, which passed very near to the position of mentioned float, during December 2013. This is also evident from the satellite based wind observations from OSCAT through curl of wind stress and Ekman pumping. The sub-surface chlorophyll bloom is substantiated by the surface chlorophyll-a values of MODIS during the period. Intense mixing caused due to the passage of cyclone might have resulted in mixing of subsurface waters thereby breaking the stratification of otherwise stable surface waters of Bay of Bengal, enhancing the nutrient supply, which resulted in strong chlorophyll bloom. The subsurface chlorophyll structure of Bay of Bengal and its variability during the passage of cyclone is for the first time revealed by the floats equipped with biological sensors. This work reveals the synergistic application of in-situ (Bio- Argo) and satellite data to monitor the changes in subsurface structure during the passage of cyclones

Comparison between Argo-derived sea surface temperature and microwave sea surface temperature in tropical Indian Ocean

A comparison between in situ and microwave satellite-derived sea surface temperature (SST) for the tropical Indian Ocean (TIO) during January 2009–December 2010 is presented. All available in situ temperatures close to the surface (5 m) from Argo profiling floats are used in this study. Weekly 0.25° × 0.25° spatial resolution SST was produced from these Argo in situ data using the Data-Interpolating Variational Analysis (DIVA) method. This weekly Argo sea surface temperature (ASST) is compared with Tropical Rainfall Measuring Mission Microwave Imager (TMI)-retrieved Sea Surface Temperature (TMISST) and available blended Optimum-Interpolation Sea Surface Temperature (OISST) product, at selected regions encompassing the north, central and southern TIO. The results indicate a bias and root mean square error (RMSE) of –0.02°C and 0.45°C between ASST and OISST, whereas the bias and RMSE between ASST and TMISST is observed to be 0.11°C and 0.32°C, respectively. The correlation coefficient (r) between ASST and OISST is observed to be 0.980, whereas r between ASST and TMISST is observed to be 0.985

GUI based interactive system for Visual Quality Control of Argo data

Argo program is aimed at maintaining an array of 3000 free drifting floats to measure temperature and salinity (T/S). Present study consists a PC-based system developed for visualization and quality control of T/S profiles obtained from Argo floats. The system, coded in Java, is user interactive and runs on Windows platform. Default the Argo T/S profiles pass through 19 automatic checks and quality flags are assigned. Using the system, T/S profiles that failed the automatic Argo tests undergo visual review. This visual review is done to determine whether automatic Argo tests were excessively flagging good measurements as bad or vice-versa, to motivate modifications to automatic Argo tests and to determine whether additional tests were necessary to catch problems that could not be detected by the existing tests. Visual review is done by comparing with 1° X 1° monthly climatologies from WOA01. Profile records deviating beyond 2 standard deviations from the mean are flagged as bad. Provision is also given to compare individual T/S profiles with previous 5 profiles via a waterfall plo

INCOIS Live Access Server: A Platform for Serving the Geospatial Data of Indian Ocean

The INCOIS Live Access Server (I-LAS) was setup at Indian National Centre for Ocean Information Services to effectively deliver diversified geospatial products pertaining to Indian Ocean. The I-LAS provides free access to full suite of satellite-derived data products viz., sea surface temperature (SST), surface chlorophyll, surface wind products and number of products derived from objectively analyzed in-situ data. Further model analysis products from GODAS-MOM are also made available. Additionally climatological data sets from World Ocean Atlas 2009 are also made available for inter-comparison and generation of anomalies. Various functionalities for on the fly visualization and downloading of data are in built in to the LAS along with OpenDAP data sharing. Some examples of data usage from the LAS are also presented. It is observed that INCOIS LAS is being extensively used by various users and statistics of data usage is monitored on a regular basis and 100% uptime is maintained