Göteborg Urban Climate Group University of Gothenburg Department of Earth Sciences

SOLWEIG1D

User Manual - Version 2015a

Date: 2015 06 17

Fredrik Lindberg

Göteborg Urban Climate Group, University of Gothenburg

contact: Fredrik.lindberg@gvc.gu.se

Introduction This manual describes how to install and make use of the SOLWEIG point version that is able to

compute a number of parameters used in urban climatology and biometeorology using a Graphical

User interface (GUI). Parameters such as the Sky View Factor (SVF), Mean radiant temperature (Tmrt),

Physiological Equivalent Temperature (PET), Universal Thermal Climate Index (UCTI) and Sun

diagrams can be derived. This software is free to use.

Version history

V2015a

New option to consider standing man as a cylinder according to Holmer et al. (2015). A simple

ground cover scheme included.

V2014a

New format of meteorological input data. Bug fixed when recalculating wind based on height.

V 2013a

Minor bug fixes. Option to recalculate wind to correct height using the wind power law is included.

V 1.0

First version. Released 2012-05-21

Installation This model is written in MATLAB computing language and is executed using the MATLAB Compiler

Runtime (MCR), which can be distributed royalty free. Hence, the user can run the model without

having a MATLAB license or any skills in MATLAB programming. The MCR runs on WINDOWS

NT/2000/XP/Vista7 platforms. The current version of the MCR is 8.2(64-bit).

To be able to run the model the MCR must be installed locally on the computer that will be used. The

MCR and the SVF calculator can be downloaded from:

http://www.mathworks.se/products/compiler/mcr/

Using the Interface To run the interface the user simply needs to double click on the SOLWEIG1D.exe. The figure below

shows the design of the interface:

Figure 1. The Graphical User Interface for SOLWEIG1D, v2015a

There are a number of features that could be utilized. The user has an option to make use of a

hemispherical photograph to derive SVF and information about shadow from surrounding objects.

The calculation of Tmrt, PET and UTCI could also be performed without an hemispherical photo. The

interface then assume direct radiation from the Sun (in sun) and SVF is decided by the user manually

(default value = 0.60).

Hemispherical image processing 1. Loading image: File formats possible for image files are *.jpg,*.png, *.gif, *.tif or *.pgm.

2. Specify radius: In order to compute the radius and the center point (red star in the figure

below) of the image, three point on the circumference line has to be specified (red crosses in

the figure below). Click on the “Specify radius” and move your mouse pointer over the image.

It will turn to a cross and now you can click on three separate locations on the circumference.

Figure 2. Specifying the radius. Snapshot from version 2014a.

3. Converting image to black and white: sky and non-sky pixels has to be separated. To make this

separation as good as possible a slide-bar is available. Make sure that all sky pixels are

correctly classified.

4. Manual correction of non-sky pixels (optional): Usually, light areas such as windows and white

walls is classified as sky and this has to be corrected in order to obtain correct SVF-values. If

you have areas that are wrong classified, click on the “Fill non-sky regions”, move your mouse

pointer over the BW-image and the pointer will turn into a cross. Fill regions where you have

wrong classified by inserting vertices of a polygon as shown in the figure below. To finish a

polygon, click on the first vertices in the polygon and finally double click in the polygon. You

can fill as many polygons as possible by just clicking the “Fill non-sky regions”-button again.

Some fish eye lenses do not have 180 degree field of view. Therefore an option to change this is

included.

Sky View Factor When an image is loaded and processed, SVF can be calculated. The method of Holmer et al. (2001)

is used.

Date and time If no date and time is set, the specified time shown will be used (2012-06-21). Date and time is used

when creating Sun diagram and also when Tmrt, PET and UTCI is calculated with a data file (see

below).

Sun Diagram A feature where the position of the Sun for a specific day can be plotted is found in the right corner.

To be able to use this feature, a hemispherical photograph must be loaded and a geographical

location must be set.

Figure 3. Example of the a Sun diagram. Snapshot from version 2014a.

Geographical location There are a number of predefined locations added within the interface. Location could also be added

manually.

Personal parameters (PET) In order to calculate PET, a number of settings regarding the human body must be specified. The

default values can be altered by the user.

Urban parameters These settings are included in the calculation of the radiant fluxes which sums up the mean radiant

temperature.

Personal data (Tmrt) There are also personal settings which has to be specified when calculating Tmrt.

Meteorological data There are two different possibilities regarding what meteorological data that should be used in the

calculation. The user could either calculate a single point in time by using the values in the boxes OR

use a meteorological input data file.

As from version 2015a SOLWEIG adopts a new format of meteorological data. This is done as

SOLWEIG is planned to be incorporated in a coupled model system for climate sensitive applications.

Required inputs must be continuous – i.e. gap fill any missing data. Table 1 gives the required and

optional additional input variables. Variables marked with # in the comment column are not used with

the current version and can be replaced with -999.0 if the user’s dataset does not include the variable.

If a parenthesis is added the variable is optional. Make certain these are not TAB delimited files. By

default, the Interface will allow all types of file extensions in where the meteorological data can be

stored. In order to be successfully loaded, it has to follow the following format including the order of

the columns.

Table 1. Meteorological input data to run SOLWEIG. Model – refers to the name within the model

code.

No. USE Column name Description

1 R iy Year [YYYY] 2 R id Day of year [DOY] 3 R it Hour [H] 4 R imin Minute [M] 5 # qn Net all-wave radiation [W m-2], Required if NetRadiationChoice = 1. 6 # qh Sensible heat flux [W m-2] 7 # qe Latent heat flux [W m-2] 8 # qs Storage heat flux [W m-2] 9 # qf Anthrpogenic heat flux [W m-2] 10 # U Wind speed [m s-1] 11 R RH Relative Humidity [%] 12 R Tair Air temperature [°C] 13 O pres Barometric pressure [kPa] 14 O rain Rainfall [mm] 15 R kdown Incoming shortwave radiation [W m-2], Must be > 0 W m-2. 16 # snow Snow [mm], Required if SnowUse = 1 17 # ldown Incoming longwave radiation [W m-2] 18 # fcld Cloud fraction [tenths] 19 # Wuh External water use [m3] 20 # xsmd Observed soil moisture [m3 m-3 or kg kg-1] 21 # lai Observed leaf area index [m2 m-2] 22 O kdiff Diffuse radiation [W m-2]

23 O kdir Direct radiation [W m-2] 24 # wdir Wind direction [°]

R = Required, O = Optional, # = Net required for SOLWEIG

IMPORTANT! The direct-beam radiation (Kdir) used as input in the SOLWEIG model is not the

direct shortwave radiation on a horizontal surface but on a surface perpendicular to the light source.

Hence, the relationship between global radiation and the two separate components are:

avkdn = Kdir sin(h) + Kdiff

where h is the sun altitude. Since diffuse and direct components of short wave radiation is not

common data, it is also possible to calculate diffuse and direct shortwave radiation by ticking the box

in Figure 16 Reindl et al. (1990).

IMPORTANT! As from version 2014a, the hour time stamp is the average from the time step

before, i.e. hour 3 is the time between 2 and 3 am in an hourly time resolution is used. As from version

24014a the time resolution is not set to one hour but could change based on the input meteorological

data. As from version 2015a, the file ModelledYears.txt is excluded and information about year is

added into the meteorological file.

Leap years are taken into account and will be determined for each year. In the current version of

SOLWEIG (2015a), Daylight Savings is not used and could therefore be ignored. Examples of the input

files is found in the ‘test files’ folder.

Calculation The calculation procedure will be based on the settings made previous. If no meteorological data file

is used, the sun position for the specific time and location is shown on the image (see figure 4).

There is also a possibility to estimate diffuse and direct radiation from global radiation using the

equations presented by Reindl et al. (1990) by checking the box within the calculation panel.

Mean radiant temperature is calculated by using the equations presented in Lindberg et al. (2008)

and Lindberg and Grimmond (2011). There is no possibility to separate between buildings and

vegetation in the current version. The outgoing longwave radiation is not using a ground view factor

as presented in Lindberg and Grimmond (2011) to estimate surface temperature but is instead using

the information if the point of interest is on shadow or in direct sunlight. The Universal Thermal

Climate Index (UCTI) make use of wind speed at 10 magl whereas PET is using wind speed at the

center of gravity for a person (1.1 magl). Therefore, an option to specify at which height wind speed

is obtained is included. Wind speed is then recalculated to the height used for either UTCI or PET by

using the wind power law with a constant of 0.14. The equation below exemplifies the recalculation

of wind speed from 10 to 1.1 magl:

𝑊𝑠1.1 = (1.1

10)0.14

×𝑊𝑠10

Figure 4. Result from a calculation using the setting without a met-data file. The red circle is the position of the

Sun (snapshot from version 2014a).

Additional information and acknowledgements All components of the calculation is written to a text file which will be saved in the documents folder

in your home directory. The name of the text file will be ‘OutputData_SOLWEIGpoint_

Calculator_YYYYMMDDTHHMMSS.txt’.

The equations for plotting the Sun diagram was originally written by Brian Offerle. The equations for

the PET calculation was kindly acquired and from Jutta Holst and Helmut Mayer, University of

Freiburg. The equation for the UCTI estimation was obtained from the Cost Action 730 (UTCI,

Version a 0.002, October 2009 Copyright © 2009 Peter Broede).

References Holmer B, Postgård U, Eriksson M, (2001) Sky view factors in forest canopies calculated with IDRISI. Theoretical and Applied Climatology 68, 33-40

Holmer B, Lindberg F, Rayner D, Thorsson S, (2015) How to transform the standing man from a box to a cylinder – a modified methodology to calculate mean radiant temperature in field studies and models. ICUC9 - 9th International Conference on Urban Climate jointly with 12th Symposium on the Urban Environment.

Lindberg F, Grimmond CSB (2011) The influence of vegetation and building morphology on shadow patterns and mean radiant temperature in urban areas: model development and evaluation. Theoretical and Applied Climatology. doi: 10.1007/s00704-010-0382-8

Lindberg F, Holmer B, Thorsson S (2008) SOLWEIG 1.0 – Modelling spatial variations of 3D radiant fluxes and mean radiant temperature in complex urban settings. International Journal of Biometeorology, 52 s. 697–713.

Reindl DT, Beckman WA, Duffie JA (1990) Diffuse fraction correlation. Solar Energy 45:1-7