Greater Manchester
The Greater Manchester case study investigates urban heat exposure under current and future climate and intervention scenarios.
It is the only documented case study addressing heat rather than flooding, and the only one that runs the UrbClim and HiREx pairing.
The two-scale approach
The study combines neighbourhood-scale urban climate modelling with metre-scale heat-exposure modelling, in order to represent two things at once:
| Scale | Captures |
|---|---|
| Neighbourhood | The wider urban heat-island signal |
| Metre | Local differences in exposure caused by buildings, vegetation and shade |
Why one scale would not do
A neighbourhood-scale model can tell you a district runs several degrees warmer than the countryside around it. It cannot tell you that one side of a street is tolerable and the other is not.
Since adaptation decisions are made about specific streets, trees and buildings, the metre scale is where the intervention question actually lives. See hazard models.
How the IMP was applied
UrbClim: neighbourhood scale
UrbClim is used to simulate hourly urban meteorology over a domain centred on Greater Manchester at 200 m resolution.
It provides four variables:
| Variable | Description |
|---|---|
| Air temperature | T2M, at 2 m |
| Specific humidity | QV2M, at 2 m |
| Wind speed | WS2M, at 2 m |
| Land-surface temperature | LST |
The full output specification, including the grid, domain, projection and observed value ranges, is documented in UrbClim: generated output data. That specification is drawn from this case study.
HiREx: metre scale
HiREx uses the UrbClim meteorology together with high-resolution geometry and surface data to resolve local heat exposure at 1 m resolution.
Its inputs are:
| Input | Contributes |
|---|---|
| Building geometry | Shadows cast by buildings, and sky view factor |
| Tree-canopy data | Shadows cast by tree crowns |
| Vegetation | Surface energy behaviour |
| Sealed surfaces | Daytime heating of paving and roads |
| Water bodies | High heat capacity and evaporative behaviour |
Selecting days
Representative typical and hot summer days are selected from the UrbClim simulations.
The selection method, including the 90th-percentile reduction across urban grid cells and the two-stage screening for the hot day, is documented in HiREx: choosing representative days.
Outputs
HiREx produces black-globe-temperature outputs for different:
- Intervention scenarios
- Time horizons
- Climate scenarios
These outputs provide the heat-hazard information required for subsequent assessment of exposure and adaptation effects.
Where the adaptation link lies
Producing outputs per intervention scenario is what makes this a case study rather than a mapping exercise.
Adding trees or altering surfaces changes the geometry and surface inputs HiREx consumes, so the effect of a green adaptation measure appears directly in the black-globe temperature. See green infrastructure.
Gaps in this case study
Workflow diagram missing, and headings unfilled
The handbook indicates a diagram indicating the tools used and how they are connected, identifying inputs and outputs, as supplied for North East England. No such figure is present in the source document for Greater Manchester.
The "Tools", "Inputs per module" and "Outputs per module" headings are also present with no content beneath them.
The narrative text above is therefore the only description of how the modules connect for this case study. It covers the hazard chain, but not what happens to the heat-hazard output afterwards.
No transport modelling described
Unlike the other two case studies, this one stops at the hazard.
The narrative ends with heat-hazard information being made available for "subsequent assessment of exposure and adaptation effects", but does not describe transport demand, transport supply, agent-based simulation or performance metrics for Greater Manchester.
Whether the transport side is planned, in progress or out of scope for this case study is not stated.