.. _IntroToSOLWEIG: Thermal Comfort - Introduction to SOLWEIG ========================================= .. note:: Click `here ` to find the same tutorial as below but for data from New York City, US. Introduction ------------ In this tutorial you will use a model **SOlar and LongWave Environmental Irradiance Geometry model (SOLWEIG)** to estimate the mean radiant temperature (T\ :sub:`mrt`). SOLWEIG is a model that simulates spatial variations of 3D radiation fluxes and the T\ :sub:`mrt` in complex urban settings. It is also able to model spatial variations of shadow patterns. T\ :sub:`mrt` is one of the key meteorological variables governing human energy balance and the thermal comfort of people. It is derived from summing all the radiative (shortwave and longwave) fluxes (both direct and reflected) to which the human body is exposed. In SOLWEIG, T\ :sub:`mrt` is derived by modelling shortwave and longwave radiation fluxes in six directions (upward, downward and from the four cardinal points) and angular factors. The model requires **meteorological** forcing data (global shortwave radiation (K\ :sub:`down`), air temperature (T\ :sub:`a`), relative humidity (RH)), urban geometry (DSMs), and geographic information (latitude, longitude and elevation). To determine T\ :sub:`mrt`, continuous maps of sky view factors are required. Both vegetation and ground cover information can be added to increase the accuracy of the model output. Below, a schematic flowchart of SOLWEIG in shown. The `full manual `__ provides more detail. .. figure:: /images/SOLWEIG_flowchart.png :alt: Overview of SOLWEIG :width: 100% Overview of SOLWEIG Objectives ---------- To introduce SOLWEIG and how to run the model within `UMEP (Urban Multi-scale Environmental Predictor) `__. Help with Abbreviations can be found `here `__. Steps ~~~~~ #. Different kinds of input data, that are needed to run the model, will be generated. #. How to run the model #. How to examine the model output #. Add additional information (vegetation and ground cover) to improve the model outcome and to examine the effect of climate sensitive design Initial Practical steps ----------------------- UMEP is a python plugin used in conjunction with `QGIS `__. To install the software and the UMEP plugin see the `getting started `__ section in the UMEP manual. As UMEP is under constant development, some documentation may be missing and/or there may be instability. Please report any issues or suggestions to our `repository `__. Data for this exercise ~~~~~~~~~~~~~~~~~~~~~~ The UMEP tutorial datasets can be downloaded from our here repository `here `__. - Download, extract and add the raster layers (DSM, CDSM, DEM and land cover) from the **Goteborg folder** into a new QGIS session (see below). - Create a new project - Examine the geodata by adding the layers (*DSM_KRbig*, *CDSM_KRbig*, *DEM_KRbig* and *landcover*) to your project (***Layer > Add Layer > Add Raster Layer**). - Coordinate system of the grids is Sweref99 1200 (EPSG:3007). If you look at the lower right hand side you can see the CRS used in the current QGIS project. - Have a look at `DailyShading` on how you can visulaise DSM and CDSM at the same time. - Examine the different datasets before you move on. - To add a legend to the **land cover** raster you can load **landcoverstyle.qml** found in the test dataset. Right click on the land cover (*Properties -> Style (lower left) -> Load Style*). SOLWEIG Model Inputs -------------------- Details of the model inputs and outputs are provided in the `SOLWEIG manual `__. As this tutorial is concerned with a **simple application** only the most critical parameters are used. Many other parameters can be modified to more appropriate values, if applicable. The table below provides an overview of the parameters that can be modified in the Simple application of SOLWEIG. Data use and type abbreviations: R: required, O: Optional, N : not needed, S: Spatial, M: Meteorological, .. list-table:: Input data and parameters :widths: 30 30 5 5 30 * - **Data** - **Definition** - **Use** - **Type** - **Description** * - Ground and building digital surface model (DSM) - High resolution surface model of ground and building heights - R - S - Given in metres above sea level (m asl) * - Digital elevation model (DEM) - High resolution surface model of the ground - R\* - S - R\* if land cover is absent to identify buildings. Given in m asl. Must be same resolution as the DSM. * - Digital canopy surface model (CDSM) - High resolution surface model of 3D vegetation - O - S - Given in metres above ground level (m agl). Must be same resolution as the DSM. * - Digital trunk zone surface model (TDSM) - High resolution surface model of trunk zone heights (underneath tree canopy) - O - S - Given in m agl. Must be same resolution as the DSM. * - Land (ground) cover information (LC) - High resolution surface model of ground cover - O - S - Must be same resolution as the DSM. Five different ground covers are currently available (building, paved, grass, bare soil and water) * - UMEP formatted meteorological data - Meteorological data from one nearby observation station, preferably at 1-2 m above ground. - R - M - Any time resolution can be given. * - Latitude (°) - Solar related calculations - R - O - Obtained from the ground and building DSM coordinate system * - Longitude (°) - Solar related calculations - R - O - Obtained from the ground and building DSM coordinate system * - `UTC (h) `__ - Time zone - R - O - Influences solar related calculations. Set in the interface of the model. * - Human exposure parameters - Absorption of radiation and posture - R - O - Set in the interface of the model. * - Environmental parameters - e.g. albedos and emissivites of surrounding urban fabrics - R - O - Set in the interface of the model. Meterological input data should be in UMEP format. You can use the `Meterological Preprocessor `__ to prepare your input data. It is also possible use the plugin for a single point in time. Required meteorological data to calculate T\ :sub:`mrt` is: #. Air temperature (°C) #. Relative humidity (%) #. Incoming shortwave radiation (W m\ :sup:`2`) The model performance will increase if diffuse and direct beam solar radiation is available but the mdoel can also calculate these variables. **If Point Of Interest (POIs) is used, wind speed (m/s) is also required** (see below). How to Run SOLWEIG from the UMEP-plugin --------------------------------------- #. Open SOLWEIG from *UMEP -> Processor -> Outdoor Thermal Comfort -> Mean radiant temperature (SOLWEIG)*. - You will make use of a test dataset from observations for Gothenburg, Sweden. .. figure:: /images/SOLWEIG_Interface.png :alt: None :width: 100% :align: center Dialog for the SOLWEIG model (click on figure for larger image) #. To be able to run the model, some additional spatial datasets needs to be created. - Close the SOLWEIG plugin and open UMEP from the processing toolbox then *Pre-Processor -> Urban geometry: Sky View Factor*. - To run SOLWEIG various sky view factor (SVF) maps for both vegetation and buildings must be created (see `Lindberg and Grimmond (2011) `__ for details). - You can create all SVFs needed (vegetation and buildings) at the same time. Use the settings as shown below. Use an appropriate output folder for your computer. .. figure:: /images/SOLWEIG_Svf_solweig.png :alt: None :width: 487px :align: center Settings for the SkyViewFactorCalculator. - When the calculation is done, a map will appear in the map canvas. This is the 'total' SVF i.e., including both buildings and vegetation. Examine the dataset. - Where are the highest and lowest values found? - If you look in your output folder you will find a zip-file containing all the necessary SVF maps needed to run the SOLWEIG-model. #. Another preprocessing plugin is needed to create the building wall heights and aspect. Open UMEP from the processing toolbox again and then *Pre-Processor -> Urban geometry: Wall height and aspect* and use the settings as shown below. QGIS scales loaded rasters by a *cumulative count out* approach (98%). As the height and aspect layers are filled with zeros where no wall are present it might appear as if there is no walls identified. Rescale your results to see the walls identified (*Layer Properties > Symbology*). .. figure:: /images/SOLWEIG_wallgeight_solweig.png :alt: None :width: 505px :align: center Settings for the Wall height and aspect plugin. #. Re-open the SOLWEIG plugin and use the settings shown below. You will use the GUI to set one point in time (i.e. a summer hour in Gothenburg, Sweden) hence, no input meteorological file is needed for now. No information on vegetation or ground cover is added for this first try. Click **Run**. .. figure:: /images/SOLWEIG_Tmrt1_solweig.png :alt: None :width: 100% :align: center The settings for your first SOLWEIG run (click on figure for larger image). #. Examine the output (Average T\ :sub:`mrt` (°C). What is the main driver to the spatial variations in T\ :sub:`mrt`? #. Add 3D vegetation information by ticking *Use vegetation scheme (Lindberg, Grimmond 2011)* and add **CDSM_Krbig** as the *Vegetation Canopy DSM*. As no TDSM exists we estimate it by using 25% of the canopy height. Leave the tranmissivity as 3%. Tick *Save generated Trunk Zone DSM* (a tif file, **TDSM.tif**, will be generated in the specified output folder and used in a later section: **Climate sensitive planning**). Also tick *Save generated building grid* as this will be needed later in this tutorial. Leave the other settings as before (Step 4) except for changing your output directory, otherwise results from your first run will be overwritten. Run the model again and compare the result with your first run. #. Add your last spatial dataset, the **land cover** grid by ticking *Use land cover scheme (Lindberg et al. 2016)*. Run and compare the result again with the previous runs. Using meteorolgical data and POIs --------------------------------- SOLWEIG is also able to run a continuous dataset of meteorological data. You will make use of a single summer day as well as a winter day for Gothenburg, Sweden. The GUI is also able to derive full model output (all calculated variables) from certain points of interest (POIs). #. First you need to create a point vector layer to store the POIs. Go to *Layer > Create Layer > New Shape file*. Choose *Point* as *Type* and add a new text field called **name**. Name the new layer **POI_Kr.shp**. Specify the coordinate system as SWEREF99 12 00 (EPSG: 3007). #. Now you should add two points within the study area. To add points to the layer it has to be editable and *Add Feature* should be activated. .. figure:: /images/SOLWEIG_Addpoint.png :alt: None :width: 411px :align: center Settings to add points Two points should be added and the attributes should be id=\ **1** and name=\ **courtyard** for the right point and id=\ **2** and name=\ **park** for the left point. See figure below for the locations of the two points. .. figure:: /images/SOLWEIG_Pointskr.png :alt: None :width: 100% :align: center Location of the two POIs When you are finished, save layer edits (box in-between the two marked boxes in Figure 6). Close the editing by pressing *Toggle editing* (the pencil). #. Now open the SOLWEIG plugin. Use both the vegetation and land cover schemes as before. This time, tick in *Include POI(s)*, select your point layer and use the ID attribute as *ID field*. #. Tick in *Use continuous meteorological dataset* and choose **gbg19970606_2015a.txt** as *Input meteorological file*. Also, tick in to save T\ :sub:`mrt` (in the *Output maps* section of the dialogue box). Run the model again. Examine your output with SOLWEIG Analyzer ----------------------------------------- To perform a first set of analysis of your result you can make use of the SOLWEIG Analyzer plug-in. #. Open the Analyzer located in *UMEP -> Post-Processor -> Outdoor Thermal Comfort -> SOLWEIG Analyzer*. Here you can analyze both data from your POIs as well as perform statistical analysis based on saved output maps. Start by locating your output folder in the top section (*Load Model Result*). .. figure:: /images/SOLWEIG_SOLWEIGAnalyzer.png :alt: None :width: 100% :align: center Dialog for the SOLWEIG Analyzer plug-in #. Firstly you will compare differences in T\ :sub:`mrt` for the two locations (courtyard and park). This can done using the left frame (*Point of Interest data*). Specify *courtyard* (1) as the *POI* and *Mean Radiant Temperature* as the *variable* in the two top scroll down lists. Then tick in *Include another POI/variable* and chose *park* (2) and *Mean Radiant Temperature* below. Click *Plot*. What explains the differences? #. Now lets move on to analyse the output maps generated from our last model run. In the right frame, specify *Mean Radiant Temperature* as *Variable to visualize*. Start by clicking *Show Animation*. Now the output maps of T\ :sub:`mrt` generated before are displayed in a sequence. #. The next step is to generate some statistical maps from the last model run. Specify *Mean Radiant Temperature* as *Variable to visualize* and tick *Exclude building pixels*. Choose the building grid that you saved earlier in this tutorial. If it is not in the drop-down list you need to add this layer (**buildings**) to your project. Tick in *T*\ :sub:`mrt` *Percent of time above threshold (degC)* and specify **55.0** as threshold. Specify an output folder and also tick *Add analysis to map canvas* before you generate the result. The resulting map show the time that a pixel has been above 55 degC based on the whole analysis time i.e. 24 hours. This type of map can be used to identify areas prone to heat stress, for example. Climate sensitive planning -------------------------- Vegetation is one effective measure to reduce areas prone to heat related health issues. In this section you make use of the Tree Generator plugin to see the effect of adding more vegetation into our study area. The municipality in Gothenburg have identified a "hot spot" south of the German church and they want to see the effect of planting three new trees in that area. The Tree Generator ~~~~~~~~~~~~~~~~~~ The Tree Generator plugin makes use of a point vector file including the necessary attributes to generate/add/remove vegetation suitable for either mean radiant temperature modelling with SOLWEIG or urban energy balance modelling with SUEWS. #. Create a point vector shape file named (**TreesKR.shp**), as described in the previous section, adding five attributes (*id, ttype, trunk, totheight, diameter*). The attributes should all be decimal (float) numbers (see table below). The location of the three new trees are shown in figure below. The values for all three vegetation units should be **ttype=2, trunk=4, totheight=15, diameter=10**. .. figure:: /images/SOLWEIG_File_TreesKR.png :alt: None :width: 100% :align: center Location of the three new vegetation units. #. Add your created trunk zone dsm (**tdsm.tif**) that was created previously (located in your output directory). #. Open the TreeGenerator (*UMEP > PreProcessor > Spatial Data > TreeGenerator*) and use the settings as shown in figure below. .. figure:: /images/SOLWEIG_Treegeneratorsolweig.png :alt: None :width: 411px :align: center The settings for the Tree Generator #. As the vegetation DSMs have been changed, the SVFs have to be recalculated. This time use the two generated vegetation DSMs. #. Re-run SOLWEIG using the same settings as before but now use the new vegetation surface models as well as the new SVFs generated in the previous step. #. Generate a new, updated threshold map based on the new results and compare the differences. The table below show the input variables needed for each tree point. +-----------------------+-----------------------+-----------------------+ | Attribute name | Name | Description | +=======================+=======================+=======================+ | ttype | Tree type | Two shapes are | | | | available: | | | | | | | | - conifer = 1 and | | | | - deciduous = 2. | | | | - To remove | | | | vegetation set | | | | ttype = 0. | +-----------------------+-----------------------+-----------------------+ | trunk | Trunk zone height (m | Height of the trunk | | | agl) | zone. | +-----------------------+-----------------------+-----------------------+ | totheight | Total tree height (m | Maximum height of the | | | agl) | vegetation unit | +-----------------------+-----------------------+-----------------------+ | diameter | Canopy diameter (m) | Circular diameter of | | | | the vegetation unit | +-----------------------+-----------------------+-----------------------+ Tutorial finished.