Oklahoma Mesonet

1
Drought and the Modernized Cooperative Observer
Network Derek S. Arndt, Mark A. Shafer and
Kenneth C. Crawford Oklahoma Climatological Survey

• Some prominent users of OCSs drought package
• U.S. Drought Monitor Authors
• Oklahoma Water Resources Board
• (lead agency in OK state drought task force)
• Oklahoma Fire Marshall and Governors Office
• (red flag alerts, burn bans, etc.)

Oklahoma Mesonet
Oklahoma Climatological Survey
OCS Drought Monitoring Philosophy Six Guiding
Principles For nearly ten years, OCS has
monitored drought conditions with an expanding
suite of real-time observations and products.
Self-assessment using feedback from clients
helped forge a drought monitoring philosophy. The
following six tenets guide the ongoing
development of OCS drought monitoring
efforts 1. Drought is a social phenomenon A
widely accepted definition of drought is
deceptively simple It occurs when there is not
enough water available to meet needs (Redmond
2002). This innocent definition dictates that
responsible decision-makers, and those who
provide their information, approach an
understanding of drought through the lens of
these needs. 2. Drought is relative in time,
space and application Drought assessment must
consider an ongoing interplay between scales. In
Oklahoma, three intensifications of drought
conditions occurred in the last five years
summer 1998 (6 months with statewide impacts),
late summer 2000 (2 months with statewide
impacts), and 2001-02 (12-14 months, greatest
impact in states western half). Were these three
separate events? Yes and no. To the state Fire
Marshall, they were three separate and severe
events that exacerbated wildfire conditions. To
winter wheat farmers, they were three separate
events whose impacts varied due to the time of
year. To reservoir operators in southwestern
Oklahoma, the period was essentially a single
multi-year episode of varying intensity.
Reservoir levels dropped and failed to recover
throughout the period. 3. Because drought is
intimately tied to society, a long-term reference
is vital Society adjusts to nature over
generations, and drought represents a departure
of varying significance from natures long-term
signal. Long-term averages are a major component
of virtually all drought assessment indices,
whether in the form of 30-year normals (e.g., for
the Palmer Index) or the entire long-term record
(e.g., for the Standardized Precipitation
Index). Because people adjust, an objective
measure of drought may have different impacts
over time. For example, lessons learned during
the great droughts of the 1930s radically changed
farming practices in the Plains. As a result, the
impacts of the multi-year 1950s drought in
Oklahoma were less severe, even though objective
measures indicate a severity on par with the
1930s. 4. New and emerging observational
datasets should be explored Soil moisture
observations from the Oklahoma Mesonet show a
promising contribution to drought monitoring in
the state. The ability to see both topsoil and
subsoil moisture conditions provides a valuable
verification tool that is measured independently
of other drought-related variables. The
observations are particularly effective during
drought recovery, when they yield guidance on
which precipitation events provide deep relief
and which infiltrate just a few inches below the
surface. The soil moisture dataset also offers
opportunities for drought-related research.
Decomposing long-term events into individual
episodes of precipitation and drying will isolate
the building blocks of drought and recovery. 5.
Drought is a multi-faceted issue and requires a
multi-faceted assessment Assessing drought is
much like assessing illness more than one type
of assessment is often necessary. A doctor does
not make a diagnosis based on one temperature
measurement. Instead, the doctor may use that
observation along with the results of other
patient-appropriate and symptom-appropriate
tests. That is, the doctor uses a well-chosen
indicator in concert with other well-chosen
indicators. A responsible drought decision-maker
(and those who supply his data) should take the
same approach. 6. Deliver drought information,
not just drought data An independent survey of
about 100 Oklahoma drought decision-makers
indicated that real-time information
significantly improves their drought decision
process. However, many respondents believed that
large doses of data become cumbersome if provided
without any context of experience or history.
Simply put, as the technology associated with
delivering high-quality drought data improved,
the ability to overwhelm clients with volumes of
numbers became a real problem. Finding the best
balance between data volume and usability is an
ongoing effort at the Climate Survey. Because
many drought managers are from non-meteorological
or even non-scientific fields, OCS conveys
information with sensitivity to the varying ways
that adults process it. From an information
perspective, several components of OCSs drought
information suite overlap, with the anticipation
that at least one will resonate with the
particular learning style and experience base of
a client.
Ten seasons are updated daily to provide the most
appropriate time-scale for the client.
Rankings and comparisons provide valuable
historical perspective
Basic statistics give a traditional view of the
seasons precipitation
Because many drought decision makers come from
outside the geosciences, online help is available
for each OCS drought product.
Historical extremes provide context of
possibility for the client
Analog seasons appeal to personal and
institutional memory.
Drought indices provide trigger information for
topsoil and subsoil interests
Finding the best balance between data volume and
usability is an ongoing effort at the Oklahoma
Climatological Survey.
Modeled fire danger and smoke management tools
for fire personnel
Summary maps provide at-a-glance assessment of
statewide conditions
Detecting a False Recovery September 2003 brought
rain to drought-stricken parts of north central
Oklahoma, ending extreme wildfire conditions and
offering promise to the wheat farmers that
comprise a large component of the regions
economy. Short term rainfall (30 days, upper
left) and near-surface soil moisture (5 cm, lower
left) suggested wet conditions across the region
in mid-October. However, longer-term rainfall
(120 days, upper right) and deeper soil moisture
(75 cm, lower right) revealed that deep
replenishment had not occurred in many areas. The
scenario suggested a vulnerability to drought
relapse if rains ceased, which was indeed the
case. Seed that germinated rapidly in the shallow
moisture was unable to access deeper soil water.
This stunted early root and plant growth, which
are very important to yield.
Basic statistics can be misleading! In the above
case, similar percent-of-normal values mask
vastly different departures from historical
norms. OCS drought products supply historical
perspective alongside basic statistics.
http//climate.ocs.ou.edu/rainfall_update.html