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BITMAP: Tracks of western disturbances transiting Pakistan and north India from various CMIP5 Historical experiments

Update Frequency: Not Planned
Latest Data Update: 2019-03-07
Status: Completed
Online Status: ONLINE
Publication State: Citable
Publication Date: 2019-03-18
DOI Publication Date: 2019-03-18
Download Stats: last 12 months
Dataset Size: 23 Files | 266MB


This dataset contains tracks generated using a bespoke tracking algorithm developed within the BITMAP (Better understanding of Interregional Teleconnections for prediction in the Monsoon And Poles) project, identifying and linking upper-tropospheric vortices (described in Hunt et al, 2018, QJRMS - see linked documentation). This utilised data derived from from various simulation output for the WCRP Coupled Model Intercomparison Project, Phase 5 (CMIP5) 'Historical' experiment. Similar datasets were produced using various model output from the WRCP CMIP5 'RCP45' and 'RCP85' experiments and the ECMWF ERA-Interim reanalysis model output, also available within the parent dataset collection.

Western disturbances (WDs) are upper-level vortices that can significantly impact the weather over Pakistan and north India. This is a catalogue of the tracks of WDs passing through the region (specifically 20-36.5N, 60-80E) on the 500 hPa layer. This differs from those tracks from the ECMWF Era-Interim data which were carried out on the 450-300 hPa layer. See linked documentation for details of the algorithms used.

BITMAP was an Indo-UK-German project (NERC grant award NE/P006795/1) to develop better understanding of processes linking the Arctic and Asian monsoon, leading to better prospects for prediction on short, seasonal and decadal scales in both regions. Recent work had suggested that the pole-to-equator temperature difference is an essential ingredient driving variations in the monsoon. For further details on the project itself see the linked Project record.

Citable as:  Hunt, K.; Turner, A.G.; Shaffrey, L.C. (2019): BITMAP: Tracks of western disturbances transiting Pakistan and north India from various CMIP5 Historical experiments. Centre for Environmental Data Analysis, 18 March 2019. doi:10.5285/f2ab8c5fb8da40cf96d32ac3739149ca.
Abbreviation: Not defined
Keywords: Pakistan, India, Western disturbances, Vortices


Previous Info:
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Access rules:
Access to these data is available to any registered CEDA user. Please Login or Register for an account to gain access.
Use of these data is covered by the following licence: When using these data you must cite them correctly using the citation given on the CEDA Data Catalogue record.
Data lineage:

Data produced and prepared for archiving by the authors before supplying to the Centre of Environmental Data Analysis (CEDA) for use by the research community.

Data Quality:
The user is referred to Hunt et al. (2018, QJRMS) for a full description of the tracking algorithm and statistics of the dataset.
File Format:
Data are BADC-CSV formatted.

Process overview

This dataset was generated by the computation detailed below.

BITMAP: Western Disturbance Tracks Algorithm


Tracks generated using a bespoke tracking algorithm, identifying and linking upper-tropospheric vortices (described fully in Hunt et al, 2018, QJRMS - see linked documentation to this record), using data derived from ERA-Interim reanalysis data and selected CMIP5 model runs (with some modifications such as the vorticity level used).

In essence the algorithm works by:

1. locating all mid-tropospheric relative vorticity maxima;

2. group multiple peaks by using a neighbourhood filter, then integrate to find the parent vortex centre;

3. link potential candidates together across time steps to form tracks using a nearest-neighbour approach incorporating local wind speed;

4. surviving tracks are filtered by duration (> 2 days) and location (must pass through [20-36.5N, 60-80E]).

Input Description


Output Description


Software Reference


  • long_name: area integral of relative vorticity
  • long_name: date-time of the event
  • long_name: eccentricity
  • standard_name: atmosphere_absolute_vorticity
  • long_name: event vorticity
  • long_name: latitude
  • long_name: longitude
  • long_name: radius of gyration of fitted Gaussian profile
  • long_name: signal-to-noise ratio
  • long_name: unique id assigned to each timestep
  • long_name: unique id assigned to each track

Co-ordinate Variables

Temporal Range
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