fieldset ( fieldset op fieldset )
...
Interpolate a fieldset at a given point. The method used is bilinear interpolation. If a list is given, it must contain two numbers - latitude and longitude. If two numbers are given, the first is the latitude, the second the longitude. The field must be a gridded field. If the fieldset has only one field, a number is returned; otherwise a list is returned. Where it is not possible to generate a sensible value due to lack of valid data in the fieldset, nil is returned. Note that a similar function, nearest_gridpoint() , also exists.
geopoints interpolate ( fieldset,geopoints )
Generates a set of geopoints from a field. The first field of the input fieldset is used. The field is interpolated for each position of the geopoints given as a second parameter. The method used is bilinear interpolation. The output geopoints take their date, time and level from the fieldset. Where it is not possible to generate a sensible value due to lack of valid data in the fieldset, the internal geopoints missing value is used (this value can be checked for with the built-in variable geo_missing_value or removed with the function remove_missing_values). Note that a similar function, nearest_gridpoint() , also exists.
vector or list latitudes ( fieldset )
...
The list parameter must contain exactly four numbers representing a geographical area. These numbers should be in the order north, west, south and east (negative values for western and southern coordinates). Non-rectangular masks, and even convex masks can be created by using the operators and , or and not . To create the following mask :
First decompose into basic rectangles :
...
Then create a mask for each of them and use and and or to compose the desired mask. This is the corresponding macro :
# Define basic rectangles
a = [50,-120,10,-30]
b = [20,20,50,10]
c = [50,50,40,100]
d = [35,-60,-40,100]
# The field is used to get the grid information
f = retrieve(...)
# First compute the union of a,c and d
m = mask(f,a) or mask(f,d) or mask(f,c)
# Then remove b
m = m and not mask(f,b)
...
Returns the value of the nearest point to a given location (or locations) in each field of a fieldset. The field must be a gridded field. If a list is given, it must contain two numbers - latitude and longitude. If two numbers are given, the first is the latitude, the second the longitude. For batch processing of multiple locations, two vectors can be given given, the first is a vector of latitudes, the second the longitudes; this can be much more efficient than multiple calls with a single location each. If the fieldset has only one field, a number (or vector) is returned; otherwise a list of numbers (or a list of vectors) is returned. Where it is not possible to generate a sensible value due to lack of valid data in the fieldset, the a nil is returned in the case of a single coordinate, or vector_missing_value in the case of a vector. Note that a similar function, interpolate() , also exists.
geopoints nearest_gridpoint ( fieldset,geopoints )
Generates a set of geopoints from a field. The first field of the input fieldset is used. The result is a set of geopoints whose values are those of the nearest gridpoints in the field to the geopoints given as a second parameter. Where it is not possible to generate a sensible value due to lack of valid data in the fieldset, the internal geopoints missing value is used (this value can be checked for with the built-in variable geo_missing_value or removed with the function remove_missing_values). Note that a similar function, interpolate() , also exists.
list nearest_gridpoint_info ( fieldset,list )
list nearest_gridpoint_info ( fieldset,number,number )
...
The following example computes the total amount of liquid water in the atmosphere by integrating the cloud liquid water content (clwc ) over all levels of the model :
# Retrieve clwc
clwc = retrieve(
levtype : "ml",
levelist : [1,"to",31],
param : "clwc",
date : -1,
grid : [2.5,2.5]
)
# Retrieve lnsp
lnsp = retrieve(
levtype : "ml",
levelist : 1,
param : "lnsp",
date : -1,
grid : [2.5,2.5]
)
# Integrate the field
x = vertint(lnsp,clwc)
plot(x)