Being combination of direct observation for the date short-term hindcast and forecast in reference to the date when observation is compiled Nowcast can be defined as best known information in the region for that particular day when it was compiled. This dataset is an enhanced ice egg chart of the day summarizing all the best available information for that particular day for which it was compiled. It includes:
- Highly reliable ice classification from SAR images;
- Interpretation from usable and partly usable optical data;
- Modelled data for areas that were not covered with satellite images based on the interpretation of images from previous or next day under assumed action of weather conditions that affected the area before or after reporting period.
The major purpose of compiling this dataset is having a regular and temporally coarse enough dataset to track changes resulting from corresponding Metocean conditions. The dataset is also easily analyzable statistically as there is no gaps in information both spatially and temporally with infill and modelling performed during ice analysis.
Data is stored in standard shapefiles with categories and coding according to SIGRID-3 format used for exchange of ice information (WMO, 2004). In other words, attributes are a more complicated version of an Ice Egg that is used by majority of ice charting agencies in the world. In addition to standard fields in the dataset each polygons’ attributes are enhanced with additional fields characterizing ice thickness and mobility.
Iceman.kz utilizes MANICE by Canadian Ice Service being Manual for Ice Observations by Canadian Ice Service to produce Ice Analysis in a standard and comparable manner. Quality checks and means of quality assurance are in built into the plugin used to categorize ice cover. These are both basic rules that, for example, ensure total concentrations always equals sum of partials or means of automation when Stage of Development is chosen from list to correspond to Ice Thickness value.
|Regional Nowcast Analysis Samples from the Caspian Sea|
Mobility attribute assigned to polygons of similar ice conditions in this Nowcast Dataset is not standard WMO parameter and is normally not regulated with any other external standards and procedures. However, this data was widely used in the Caspian Sea for support of marine operations. The major purpose of the dataset is forecast and risk analysis of hazardous ice events for marine transport. Table below lists the attributes recorded as mobility definition for each parameter and their practical meaning for operational risk analysis and ice forecasting.
|Mobile||The area comprises of mobile ice. Comparison with adjacent in time images clearly shows ice displacement (distinctive floes, cracks, etc)||This is where majority of drift displacement observations discussed below is recorded. For operations and strategic planning one can conduct risk assessment of operations sensitive to ice movement. For example, lighter vessels being affected with side drift while in confined drained channel may be pushed off the channel to ground in surrounding shallows. Percentage of season duration in mobile conditions can be derived from this dataset for a point of interest. Applying additional filters based on drift speed and direction characterizing unfavourable conditions for operations one can estimate probability of occurrence of hazardous conditions|
|Stationary||The area was recorded mobile during the previous day, but comparison to the current analysis shows no evident displacements. It is not evident for that day of analysis, if the area is stabilized or there is just not enough wind force, or the direction is not favourable to initiate drift||Areas with this attribute are an intermediate stage between mobile and compacting that is defined with uncertainties. Generally, it is not clear from remote sensing data exactly why there is no ice drift. As there is no ridging and destroying floes it is not possible to state that compaction takes place, but in the same time there still can be some pressure in the area, but just not enough to cause deformations. With the number of years of observations, it is possible to get some understanding on the reasons why it happens. For example, in the Caspian we have defined a certain threshold for wind directions and force that distinguishes stationary from compacting at low rates, but this needed vessel reports from the transiting vessels.|
|Semi Stable||The previous situation persists for three days, but there was still no evidence that wind with sufficient force to cause drift in favourable direction occurred to initiate drift||Typically, one would have to consider different risks to operations for these areas. For example, if we take the cell with Sabetta and apply your rubble generation model we can derive long term statistics for the periods when rubble becomes operationally unacceptable. It means for long term (a month or two) forecasting based on classification of season severity you can with certain probability build an insight when you will start having troubles with operations in the area of forecast|
|Stable||Area did not move for more than 5 days and/or there is evidence that there was sufficient force wind in favourable direction||Typically, one would have to consider different risks to operations for these areas. For example, if we take the cell with Sabetta and apply your rubble generation model we can derive long term statistics for the periods when rubble becomes operationally unacceptable. It means for long term (a month or two) forecasting based on classification of season severity you can with certain probability build an insight when you will start having troubles with operations in the area of forecast|
|Compacting||There are obvious signs of compaction in the area with ice cover deformations (break up of floes, ridging, rafting)||These areas have direct impact on vessel operations (reduction of speed due to ridge ramming mode, side pressure and generally heavy ice conditions). In daily operations for route planning if the plan is traverse the area it is most wise for example to check the weather forecast and if there is possibility that the wind will change in the near future just wait and traverse when the pressure is relieved. For strategic planning the history of compaction can be used to redefine dredged channels configuration for example|
To expand on the table above favourable wind direction to initiate drift is normally such direction that drags ice seawards or towards neighboring areas with lower concentration or ice with significantly lower ice thickness. Following the logic unfavourable wind direction is towards coast or stable ice areas. Such wind will normally result with compacting or stationary ice conditions depending on wind force.
|Mobility Analysis Samples from the Caspian Sea|
Statistical analisys and summary data of othese observations for the Caspian Sea is published on our Ice&Met Dashboard. Please, use with caution. We advise to consult with our specialists before driving any conclusions that have operational or financial effects.
Our personnel is easy to engage on conversations to discuss this matter. Please, let us know if you have questions or would like to receive clarifications on data usage and possible collaboration.