Purpose of Validating a Nature Run
To determine whether or not a particular nature run is an adequate
candidate as a truth data set for OSSE's, a thorough assessment
of its 4-dimensional characteristics must be made. Identifying
and documenting the nature run's characteristics will help
interpret future OSSE results, determine if the degree of realism
is sufficient to act as proxy for the real atmosphere, and
help uncover any data transfer, unpacking, or processing errors
that may be inadvertently introduced.
The most relevant and essential attribute of the nature run for its
use in OSSE's is its realism. Therefore, investigating the
resemblance a nature run has to the real atmosphere is the
primary objective of the validation effort. Synoptic and statistical
comparison of the structure of the nature run atmosphere and
its embedded features with a range of real observations, analyses,
or climatologies is performed as part of the validation. Ideally,
the response of the data assimilation system and forecasts
from the introduction of simulated observations, extracted
from a nature run atmosphere, must be as close as possible
to the response of ntroducing similar real observations into
the same DAS and forecast system. A realistic nature run helps
to ensure this.
Concerns over the use of an operational model to generate such a long
nature run dataset, the adequacy of the nature run clouds and
cloud- related fields, and the ability of the nature run to
realistically resolve important synoptic features such as tropical
cyclones and fronts are some of what drives the need for validation.
Any important weather features that cannot be resolved properly
by the nature run will not be sampled, analyzed, and forecasted
properly by the OSSE and therefore impact on these features
cannot be examined as part of the assessment of a new instrument.
This may lead to biases in the capabilities of the instrument
and result in unrealistic expectations of its impact on numerical
weather prediction when eventually introduced into the real
observing network.
Validation of T511 Nature Run
+ South American Monsoon
+ Examples of Intense Cyclones
+ African Monsoon and Tropical Atlantic
+ Extratropical Cyclone Statistics
+ Tropical Atlantic Synoptic-Dynamic
Evaluation |
