Statistical downscaling methods

  • How does downscaling work?

    Video downscaling is the opposite of upscaling.
    It is used to decrease the resolution of a video signal.
    This is typically done when you have a video source that has a higher resolution than the display device you are using..

  • How to do downscaling?

    General steps

    1. Determine which time series you want to downscale and which climatology dataset you will downscale to
    2. Calculate changes in the monthly time series (temperature or precipitation) in relation to the time series average climate during the time period for which the climatology is available

  • What are downscaling methods?

    Downscaling techniques can be divided into two broad categories: dynamical and statistical.
    Dynamical downscaling refers to the use of high-resolution regional simulations to dynamically extrapolate the effects of large-scale climate processes to regional or local scales of interest..

  • What is downscaling data?

    Downscaling involves disaggregation coarse resolution data with the help of mathematical tools for identifying the impacts of climate change to a regional scale; outputs from global climate models have to be downscaled (Semenov and Barrow, 1997)..

  • What is statistical and dynamical downscaling models?

    Statistical downscaling and dynamical downscaling are two approaches to generate high-resolution regional climate models based on the large-scale information from either reanalysis data or global climate models.
    In this study, these two downscaling methods are used to simulate the surface climate of China and compared..

  • What is the downscaling approach?

    Downscaling is any procedure to infer high-resolution information from low-resolution variables.
    This technique is based on dynamical or statistical approaches commonly used in several disciplines, especially meteorology, climatology and remote sensing..

  • What is the statistical downscaling approach?

    For Statistical downscaling, a statistical relationship is developed between the historic observed climate data and the output of the climate model for the same historical period.
    The relationship is used to develop the future climate data.
    Statistical downscaling can be combined with bias correction/adjustment..

  • Downscaling is any procedure to infer high-resolution information from low-resolution variables.
    This technique is based on dynamical or statistical approaches commonly used in several disciplines, especially meteorology, climatology and remote sensing.
  • However, downscaling of temporal sequences, extremes in daily precipitation, and handling of nonstationary precipitation in future conditions are considered common challenges for most statistical downscaling methods.
  • Statistical Downscaling Models (SDSM) is a regression based downscaling model, which develops quantitative relationships between predictors and predictands.
    The predictors are GCM variables, for example, Geopotential height, Mean Sea Level Pressure, and predictands are temperature, precipitation, etc.
Statistical downscaling first derives statistical relationships between observed small-scale (often station level) variables and larger (GCM) scale variables, using either analogue methods (circulation typing), regression analysis, or neural network methods.

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How do you use statistical downscaling?

The relationship is used to develop the future climate data.
Statistical downscaling can be combined with bias correction/adjustment.
A tool to do this has been developed by Wageningen University and can be downloaded here. linear regression is a simple widely used method for bias correction.

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Method 1: Statistical Downscaling Using Delta Addition

The difference between present and future simulations are added to the present observation - See Plot 1 below.
First, the mean difference between present simulation (green) and future simulation (red) is calculated.
And the calculated difference is added to the present observation (blue) to make a downscaled future prediction.
In this method, only .

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Method 3: Statistical Downscaling Using Quantile Mapping

In this method, biases are calculated for each percentile in the cumulative distribution function from present simulation (blue).
Then the calculated biases are added to the future simulation to correct the biases of each percentile.
Edit the MPI_tas_JJA.yaml to change the downscaling method to 3 (quantile mapping).
Compile and run the statistical .

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What are the different types of meteorological downscaling methods?

Wilby and Wigley placed meteorological downscaling techniques into four categories:

  1. regression methods
  2. weather pattern-based approaches
  3. stochastic weather generators
  4. which are all statistical downscaling methods
  5. limited-area modeling (which corresponds to dynamical downscaling methods )
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What is the difference between BC and other downscaling methods?

BC applies a bias correction to the selected statistics, whereas the other three downscaling methods return a modified precipitation time series.
BC utilises a direct downscaling strategy by applying the relative change factors directly to the dry-spell-related research indicators.

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Which statistical downscaling methods are used in gridded observations over China?

In this study, four widely used statistical downscaling methods, BCSD, BCCI, BCCAQ and CDF-t, are evaluated via a comparison with gridded observations over China for the present climate (1961–2005), as applied to seven GCMs from CMIP5.

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Why Do We Need to Downscale GCM outputs?

Global climate models (GCMs) cannot simulate climate at the local to regional scale. - delta method - bias correction - spatial disaggregation (BCSD) - quantile mapping - asynchronous regression approach

Procedure to infer high-resolution information from low-resolution variables

Downscaling is any procedure to infer high-resolution information from low-resolution variables.
This technique is based on dynamical or statistical approaches commonly used in several disciplines, especially meteorology, climatology and remote sensing.
The term downscaling usually refers to an increase in spatial resolution, but it is often also used for temporal resolution.
This is not to be confused with image downscaling which is a process of reducing an image from a higher resolution to a lower resolution.

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