MARS requests for some parameters will also be affected by the migration to GRIB2.
Changes to param keyword
For GRIB1 parameters, the param keyword in the mars request can be set to param=indicatorOfParameter.table2Version. Requests with this structure will not work for GRIB2 as these two keys do not exist in this edition. The paramId must be used for GRIB2 parameters. This is the recommended way of specifying parameters in MARS requests.
...
| Warning |
|---|
| The following MARS retrieval is provided only as an example of the sort of change that users will need to make once the data are provided in GRIB2. If this request is run at the moment, it will return data encoded in GRIB1. |
| Retrieval of U-component of 10m wind in GRIB1 | Retrieval of U-component of 10m wind in GRIB2 |
|---|
| HTML |
|---|
<pre>
retrieve,
class=od,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=sfc,
<b><font color="red">param=165.128</font></b>,
target="output_10u.grib1"
<pre> |
|
| HTML |
|---|
<pre>
retrieve,
class=od,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=sfc,
<b><font color="red">param=165</font></b>,
target="output_10u.grib2"
<pre> |
|
Changes for parameters archived with levtype=sol
Parameters on surface levels will be archived with levtype=sol (surface other levels).
...
| Warning |
|---|
The levtype=sol keyword for multi-layer snow depth parameters in GRIB2 has been introduced with the Implementation of IFS Cycle 48r1. |
| Retrieval of snow depth in GRIB1 | Retrieval of snow depth in GRIB2 |
|---|
| HTML |
|---|
<pre>
retrieve,
class=od,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
<b><font color="red">levtype=sfc</font></b>,
<b><font color="red">param=141.128</font></b>,
target="output_sd.grib1"
<pre> |
|
| HTML |
|---|
<pre>
retrieve,
class=od,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
<b><font color="red">levtype=sol</font></b>,
<b><font color="red">levelist=1/2/3/4/5</font></b>,
<b><font color="red">param=228141</font></b>,
target="output_sd.grib2"
<pre> |
|
Addition of new MARS keyword chem for retrieval of chemical species
Another example are chemical parameters. Besides using the MARS keyword param in the request to specify the parameter type, e.g., mass mixing ratio, an additional MARS keyword chem will be used to specify the chemical substance(s), e.g., nitrogen dioxide.
| Warning |
|---|
The following MARS retrieval is provided only as an example of the sort of change that users will need to make once the data are provided in GRIB2. The values taken by the chem keyword are not yet finalised.
|
| Retrieval of NO2 mass-mixing ratio in GRIB2 - current | Retrieval of NO2 mass-mixing ratio in GRIB2 - new |
|---|
| HTML |
|---|
<pre>
retrieve,
class=mc,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=ml,
levelist=1/to/137,
<b><font color="red">param=210121</font></b>,
target="output_no2.grib1"
<pre> |
|
| HTML |
|---|
<pre>
retrieve,
class=mc,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=ml,
levelist=1/to/137,
<b><font color="red">param=402000</font></b>, <b><font color="red"># Mass mixing ratio</font></b>
<b><font color="red">chem=no2</font></b>, <b><font color="red"># Nitrogen dioxide</font></b>
target="output_no2.grib2"
<pre> |
|
Change of MARS packing for GRIB2 parameters retrieved on a grid
GRIB2 parameters retrieved on a grid will be compressed with CCSDS. To decode these parameter, ecCodes must be linked to libaec. Alternatively, the data can be retrieved in another packing type such as grid_simple packing, which was in use for the model level GRIB2 parameters.
| Warning |
|---|
The following MARS retrieval is provided only as an example of the sort of change that users will need to make once the data are provided in GRIB2. The values taken by the chem keyword are not yet finalised.
|
| Retrieval of NO2 mass-mixing ratio in GRIB2 - current | Retrieval of NO2 mass-mixing ratio in GRIB2 - new with simple packing |
|---|
| HTML |
|---|
<pre>
retrieve,
class=mc,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=ml,
levelist=1/to/137,
<b><font color="red">param=210121</font></b>,
target="output_no2.grib1"
<pre> |
|
| HTML |
|---|
<pre>
retrieve,
class=mc,
stream=oper,
expver=1,
date=-2,
time=00:00:00,
type=fc,
step=0,
levtype=ml,
levelist=1/to/137,
<b><font color="red">param=402000</font></b>, <b><font color="red"># Mass mixing ratio</font></b>
<b><font color="red">chem=no2</font></b>, <b><font color="red"># Nitrogen dioxide</font></b>
<b><font color="red">packing=simple</font></b>, <b><font color="red"># Simple packing</font></b>
target="output_no2.grib2"
<pre> |
|
