Future Trends in the Pan American Climate Studies Sounding Network (PACS-SONET)
Michael W. Douglas, National Severe Storms Laboratory - Javier Murillo, CIMMS / University of Oklahoma
PILOT BALLOON OBSERVATIONS
http://www.nssl.noaa.gov/projects/pacs/ Pilot balloon soundings, rather than radiosonde observations, have been
made throughout the PACS-SONET life span. The main advantage of pilot
balloon observations is that they are inexpensive. Typically, a 30-gram
1. HISTORY AND EVOLUTION 2. SCIENTIFIC OBJECTIVES balloon launch, excluding labor costs, is only 5-10% that of a radionsonde
launch. To date the project has generated more than 30,000 soundings.
1.1. Original network. The fundamental overall objective of the project is to establish a long-term The graphic below shows the number of observations per month
The original PACS-SONET configuration consisted of 12 pilot balloon stations. The atmospheric sounding network for providing baseline measurements for generated by the network from April 1997 to August 2003.
stations were established during March and April of 1997 in Mexico, Nicaragua, real-time climate monitoring and for comparison with model
Costa Rica, Panama, Colombia, Ecuador and Peru. The objectives of this network development activities over the PACS domain.
1) describing the amplitude of the diurnal variation of The fundamental scientific objective of PACS-SONET is to determine both
the windfield at a number of sites. the annual cycle and interannual variability of the lower tropospheric
2) Determining the circulation anomalies associated windfield associated with the monsoon circulations over and around the
with wet and dry spells over Central America. Americas, with the aim of explaining the observed variability of
3) Determining whether large differences existed precipitation over the land regions.
between the NCEP reanalysis and observations in
data sparse regions of the eastern tropical Pacific.
1997 2.1. Relevance to PACS
Fig. 1. Map showing the original
station configuration during mid-1997.
PACS-SONET observations provide the background field to the specialized SCOPE
field experiments: The scope of PACS-SONET differs from many previous field programs in that:
1.2. Changes due to El Niño 1997-98
Due to the strong El Niño event of 1997-98, the North American Monsoon Experiment (NAME) 2004. The observations at 1) it has been expanded to a broader geographical region from northern Mexico to
observational plan was modified to extend the Puerto Peñasco and Topolobampo in northwestern Mexico are intended to Paraguay.
observational period at many stations through the end help describe the low-level flow along the Gulf of California and will be of 2) it has a relatively long duration for a field program. Initially planned for 6 months,
of October 1998 and establish additional stations in relevance for NAME. it has since been extended for a total of almost 80 months.
Ecuador and Peru to better sample conditions in the
region of anticipated heavy rainfall. Due to financial South American Low-level Jet Experiment (SALLJEX) 2002-03. The 3) communication of data is in near real-time via Internet.
reasons, some of the stations actually stopped in observations at two sites in Paraguay and 6 sites in Bolivia served as the
August 1998. Nonetheless, an unprecedented data set
1998 ramp-up network for the upper-air component of SALLJEX. 4. THE FUTURE OF PACS-SONET
was obtained to describe the wind field associated with
the developing El Niño. Fig. 2. Expanded network due EPIC 2001. The stations deployed from southern Mexico to northern Peru PACS-SONET has been extended for a second 3-year period, subject to a re-
to El Niño 1997-98
provided a context for field activities related to EPIC. evaluation of the activity and more consensus-seeking on the part of the project.
The Pan American Climate Studies Sounding Network (PACS-SONET) is a research As a first step towards renewing the direction of the activity, a meeting has very
activity funded by the NOAA’s Office of Global Programs. It has evolved from a recently been held in Paraguay in late August 2003. The meeting was intended to
regional network of 6-month duration to a hemispheric activity that has been extended develop a consensus among each of the participating institutions as how to
for a second 3-year period in 2003. 3. PACS-SONET proceed to increase the effectiveness of the PACS-SONET. All participant
countries and institutions were represented at the meeting. Preliminary
DELIVERABLES conclusions from the workshop indicate that future activities should include:
1.3. Special Mesoscale Campaign in Bolivia
Pilot balloon observations were also made at Santa Cruz, 3.1 Real-time data collection. • Radiosonde observations (PTU only) at key sites such as the Galapagos Islands,
Bolivia, as part of the special El Niño campaign. Although Ecuador. An optical theodolite would be used to track the radiosonde in order to
In addition to more observing sites, efforts have been
these were only made for 3 months they showed a strong save funds by launching inexpensive non-GPS sondes. Radiosonde observations
made to make the network a real-time data
and variable low-level jet at Santa Cruz, which had not are feasible at locations were gas is generated.
collection and distribution activity. This required
been described from observations previously. These communications to be upgraded at many sites, • Continue to support educational activities to stimulate research with the data
observations stimulated further observations from a more and the development of procedures to ensure the collected. Different options to better utilize the available funds were discussed
extensive network in Bolivia during 1999. The map at right flow of data to research institutions and to all during the workshop.
shows the pilot balloon network in Bolivia during January- 1999 interested forecasting institutions. The latter is
April 1999. Fig. 3. Pilot balloon network in
• Work with the participating institutions in designing ways to better quality control
accomplished mainly through the development of
Bolivia during Jan-Apr 1999. the data.
the project’s web page, in which the observations
are made available in real time, in the form of both • Establishment of additional sites in Peru and Brazil with help from the national
1.4. Extension of the PACS-SONET raw data and synoptic maps plotted at selected meteorological services.
program levels. The figure at right shows wind barbs from
The main benefit of the reunion of the country coordinators has been to create an
In late 1999 support was obtained for extension of pilot balloon soundings (blue) at 3 sites in Bolivia
awareness among the participants about the necessity of optimizing the available
the PACS-SONET program for an additional 3-year and one in Asuncion, Paraguay, along with winds
resources of the project to stimulate research and applied forecasting activities
period. In addition to an extension in time, the obtained from the regular radiosonde network
The impact of the additional observations throughout the region. It was emphasized that PACS-SONET is not a major source
network was expanded to a broader geographical (green).
can be appreciated from the figure and the of resources for the countries involved, rather it can serve as a framework for the
region. Pilot balloon sites have been operating in quality of the data quickly assessed by development of meteorological and climate activities in the region.
Paraguay (2) and Bolivia (6). The primary objective comparing neighbor stations.
of these additional observations was to describe the 3.2 Climate monitoring
variability of the low-level flow east of the Andes and
the circulation over the Bolivian altiplano. In Mexico, Several stations have been operating since 1997
7 sites are being operated by the Mexican navy, and just now the time series is large enough to
including two in northwestern Mexico to improve the make crude estimations of the interannual
description of the low-level flow along the Gulf of varibility. The figures show monthly means of the
California. In March 2001, one station was meridional wind at San Cristobal, Galapagos for
established in Venezuela at San Fernando de Apure,
a location in the very flat llanos north of the Orinoco
the months of May (a), July (b) and December (c).
River. The figure at right shows the current PACS- 1997-2003 Southerly cross-equatorial flow at Galapagos is
SONET configuration and other stations that have moderately strong in May and has a maximum in
been operational with financial or logistic support July-August-September. December shows the
(a) May (b) July (c) December
from the project. greatest interannual variability.