Hi,
The zenith angles at the ground and the satellite differ due to the
Earth's curvature. The method sensor_pos_losBackwardToAltitude can be
used to obtain the sensor_pos and sensor_los matching a position and
direction at the ground. However, it is a relatively new method, don't
remember for what version is was introduced.
If you don't have the method, it is a relatively simple geometrical
calculation (as long as a spherical planet is assumed).
Bye,
Patrick
On 2023-10-06 17:04, 张超 wrote:
Hi Patrick，
I have attempted to simulate brightness temperature in a one-dimensional
atmosphere and compared it with observed brightness temperature. The O-B
(observation minus background) results have shown improvement. However, in this
case, the sensor line of sight (sensor_los) is defined using scan zenith angle.
In the three-dimensional simulation, the data provided by the Fengyun satellite
specifies instrument zenith angle and azimuth angle. SensorZenith is defined as
the angle between the line connecting the center of the Earth observation pixel
and the satellite, and the line perpendicular to the zenith direction.
SensorAzimuth is defined as the angle between the line connecting the satellite
and the projection point on the ground plane, and the reference direction
(north).
SensorZenith and SensorAzimuth do not seem to correspond directly to the
sensor_los that we require in ARTS. How can I convert them to the required
variable sensor_los in ARTS? Can you provide some help?
Looking forward to your reply!Thank you!
Best wishes.
Sincerely,
ZhangChao
-原始邮件-
发件人: "Patrick Eriksson"
发送时间: 2023-10-05 03:55:05 (星期四)
收件人: "张超" ,
arts_users.mi@lists.uni-hamburg.de
抄送:
主题: Re: [arts-users] consultancy question
Hi,
Thanks for the quick reply! Regarding the first point mentioned, the
simulation is described in detail as follows. The first simulation example based on is
the artscomponents/montecarlo.arts file, with the input of 3-dimensional ERA5 contour
data including temperature, humidity, pressure, and altitude, and the absorption model
including water vapor, nitrogen, and oxygen, with the water vapor and oxygen being
MPM93 models. Then according to the product matching with the Microwave Thermometer of
Fengyun3 Satellite (MWTS) to the height and line of sight of the sensor in flight,
input to sensr_pos and sensor_los, the sensor setup adopts sensor_responseGenericAMSU.
other agendas include the surface agendas as well as the non-refractive situation of
the air. The surface is modeled using TELSEM for land and TESSEM for ocean depending on
the situation. However, the simulation results are highly biased, in the teens of K or
more. Can you please see where the problem is? Or is there any related work that you
can recommend as a reference?
My recommendation is to start with setting up a clear-sky simulation.
And focus on the channels not having a sensitivity to the surface. If
you still have problems, you have most likely an error in the input data
(check e.g. units) or a mistake when defining the absorption of gases
One more question, I would like to ask if the OEM method of ARTS2.4
is perfect, I didn't use QPACK of matlab because I am more familiar with ARTS language.
The OEM inside ARTS can do everything you can do in Qpack.
Bye,
Patrick
