hurricanebackgroundwind#

[Vxgridbackwind, Vygridbackwind, Vgridbackwind, Rgrid] = hurricanebackgroundwind(xgrid, ygrid, Vxgrid, Vygrid, xCenter, yCenter, Vt, VtAzmdir, RVmax, backwindCalcMethod, Rmax, distCalcMethod, dispout)

Description#

Calculate and add background wind velocity due to hurricane front motion to hurricane rotational wind velocity

Inputs#

xgrid: x (longitude) of points which outputs are calculated at as a [M*N] array

xgrid can be a single point or 1d or 2d array
ygrid: y (latitude) of points which outputs are calculated at as a [M*N] array

ygrid can be a single point or 1d or 2d array
Vxgrid: Hurricane wind velocity in x (East) direction as a [M*N*L] array in (m/s)

L is a number of time steps

If only background wind is required, set Vxgrid=0 and Vygrid=0
Vygrid: Hurricane wind velocity in y (North) direction as a [M*N*L] array in (m/s)

L is a number of time steps

If only background wind is required, set Vxgrid=0 and Vygrid=0
xCenter: x (longitude) of hurricane center (track) as a [L] array
yCenter: y (latitude) of hurricane center (track) as a [L] array
Vt: Hurricane central translational velocity as a [L] array in (m/s)
VtAzmdir: Hurricane center velocity azimuth (bearing) direction as a [L] array in (Degree)

azimuth (bearing) direction which is measured clockwise from the north:

0 (degree): toward North, 90 (degree): toward East, 180 (degree): toward South, 270 (degree): toward West
RVmax: Distance (radius) from hurricane center to a location of maximum hurricane wind velocity as a [L] array in (m)
backwindCalcMethod=’slosh’;: Calculation method for adding background wind velocity due to hurricane motion

background wind velocity is added to points with R<=Rmax, e.g. Chavas & Emanuel (2010), Lin & Chavas (2012)

‘no’: background wind velocity is not added to hurricane velocities

‘constant’: background wind velocity is added as constant value to hurricane velocities

‘slosh’: Background wind velocity is calculated and added using SLOSH model by Jelesnianski et al. (1992)

‘lin’: Background wind velocity is calculated and added based on Lin & Chavas (2012)
Rmax=423e3;: Maximum radius of hurricane from hurricane center in (m)

Outputs for points with R>Rmax is set to zero

Median values of Rmax is 423 km (e.g. Chavas & Emanuel 2010; Lin & Chavas, 2012)
distCalcMethod=’gc’;: Distance calculation method

‘cart’: Distances are calculated on cartesian coordinate

‘gc’: Distances are calculated on Great Circle based on Vincenty formula, Vincenty (1975)

Earth radius coonsidered as mean earth radius=6371000 m
dispout=’no’;: Define to display outputs or not

‘imagesc’: 2 dimensional plot using imagesc or imshow

‘pcolor’: 2 dimensional plot using pcolor

‘contour’: 2 dimensional contour plot, number of contour=ncolor

‘quiver’: 2 dimensional vector plot

‘no’: not display

Use dispout=’no’ if calculation mesh is not 2d array

if there is more than one time step, only the last one is plotted

if flattendata=’yes’; then dispout is set as dispout=’no’;

Outputs#

Vxgridbackwind: Hurricane wind velocity with background wind in x (East) direction on defined mesh in (m/s)
Vygridbackwind: Hurricane wind velocity with background wind in y (North) direction on defined mesh in (m/s)
Vgridbackwind: Resultant hurricane wind velocity (Vx^2+Vy^2)^0.5 with background wind on defined mesh in (m/s)

Gradient wind velocity converted to wind velocity at 10 m above surface by V=VgToVCoeff*Vg
Rgrid: Distance (radius) from hurricane center to each point on the grid

Note: Outputs has dimension of [M,N,L] where [M,N] is size of the x-y grid and [L] is number of time steps

Examples#

%EXAMPLE 1

%Creating calculation mesh
[xgrid,ygrid]=meshgrid(linspace(-98,-68,100),linspace(16,44,100));

%Longitude of Hurricane Katrine center at max velocity
longCenter=-88.6;

%Latitude of Hurricane Katrine center at max velocity
latCenter=26.3;

%Hurricane Katrina translational velocity (m/s) at max velocity
Vt=5.18467;

%Hurricane Katrina velocity azimuth (bearing) in (Degree) at max velocity
VtAzmdir=306.76219;

%Hurricane Katrina 1-min sustained maximum velocity (m/s) at max velocity
Vmax=76.5;
Vmax=Vmax-Vt; %Removing hurricane translation velocity from Vmax
Vgmax=Vmax/0.8; %Converting surface velocity to gradient velocity

%Calculating distance and angle using spherical law of cosines
Rgrid=(acos(sin(deg2rad(latCenter)).*sin(deg2rad(ygrid))+cos(deg2rad(latCenter)).*cos(deg2rad(ygrid)).*cos(deg2rad(xgrid)-deg2rad(longCenter)))).*6371000; %Radius
thetagrid=atan2(sin(deg2rad(xgrid)-deg2rad(longCenter)).*cos(deg2rad(ygrid)),cos(deg2rad(latCenter)).*sin(deg2rad(ygrid))-sin(deg2rad(latCenter)).*cos(deg2rad(ygrid)).*cos(deg2rad(xgrid)-deg2rad(longCenter))); %Azimuth in radian
thetagrid=-thetagrid+pi/2; %Converting azimuth to trigonometric direction
thetagrid=thetagrid+pi/2; %Angle of velocity vector in degree (right angle respect to radius)

%Calculating hurricane velocity at each radius using SLOSH model
RVmax=32197; %Radius from hurricane center to a location of maximum hurricane wind
Vgrid=Vgmax.*(2.*RVmax.*Rgrid)./((RVmax)^2+(Rgrid).^2); %Hurricane wind velocity at radius R
Vxgrid=Vgrid.*cos(thetagrid); %Hurricane velocity in x (East) direction
Vygrid=Vgrid.*sin(thetagrid); %Hurricane velocity in y (North) direction

[Vxgridbackwind,Vygridbackwind,Vgridbackwind,Rgrid]=hurricanebackgroundwind(xgrid,ygrid,Vxgrid,Vygrid,longCenter,latCenter,Vt,VtAzmdir,RVmax,'slosh',423e3,'gc','quiver');


%EXAMPLE 2

%Creating calculation mesh
[xgrid,ygrid]=meshgrid(linspace(-98,-68,100),linspace(16,44,100));

%Longitude of Hurricane Katrine center at max velocity
longCenter=-88.6;

%Latitude of Hurricane Katrine center at max velocity
latCenter=26.3;

%Hurricane Katrina translational velocity (m/s) at max velocity
Vt=5.18467;

%Hurricane Katrina velocity azimuth (bearing) in (Degree) at max velocity
VtAzmdir=306.76219;

RVmax=32197; %Radius from hurricane center to a location of maximum hurricane wind

Vxgrid=0; %Hurricane velocity in x (East) direction
Vygrid=0; %Hurricane velocity in y (North) direction

[Vxgridbackwind,Vygridbackwind,Vgridbackwind,Rgrid]=hurricanebackgroundwind(xgrid,ygrid,Vxgrid,Vygrid,longCenter,latCenter,Vt,VtAzmdir,RVmax,'slosh',423e3,'gc','quiver');

References#

Data

www.nhc.noaa.gov/data/
www.nhc.noaa.gov/data/hurdat/hurdat2-format-nencpac.pdf
coast.noaa.gov/hurricanes
www.aoml.noaa.gov/hrd/data_sub/re_anal.html

Chavas, D. R., & Emanuel, K. A. (2010). A QuikSCAT climatology of tropical cyclone size. Geophysical Research Letters, 37(18).

Jelesnianski, C. P., Chen, J., & Shaffer, W. A. (1992). SLOSH: Sea, lake, and overland surges from hurricanes (Vol. 48). US Department of Commerce, National Oceanic and Atmospheric Administration, National Weather Service.

Lin, N., & Chavas, D. (2012). On hurricane parametric wind and applications in storm surge modeling. Journal of Geophysical Research: Atmospheres, 117(D9).

hurricanebackgroundwind

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