The NAMMA Upstream Sounding Network over West Africa:What worked and didn’t work—and was it worth the effort? How can these observations help NAMMA studies?

Michael W. Douglas1, Javier Murillo2, Jose Galvez3, John Mejia3, and Raquel Orozco3

1NOAA/NSSL, 2OU/CIMMS, and 3OU/School of Meteorology

Between July 10 and August 10, 2006 four individuals from NSSL and CIMMS/Univ. of Oklahoma (together with one volunteer) worked in four West African countries (Mali, Senegal, Mauritania, and Guinea) to improve the sounding network for NAMMA. The objective was to rehabilitate the existing pilot balloon stations and ensure their functioning for NAMMA. To this end three sounding sites were visited in Mali, 4 in Senegal, one in Guinea, and two in Mauritania. One additional site in Guinea (Kankan) was reactivated for NAMMA but was not visited, and a radiosonde station in Conakry (Guinea) was also reactivated with supplies from another NAMMA project.

In addition to replacing defective theodolites where needed with our reconditioned theodolites, we provided training to each station in the use of software to correct errors and automatically calculate the winds on a personal computer. We also showed how to transmit the data via email where Internet existed. Most observers had extensive experience making pilot balloon observations, but the poor quality of their theodolites often limited the duration of the observations.

The enhanced NAMMA sites provided additional soundings, some in real time for NAMMA aircraft operations in Sal. Unfortunately, a number of the sites that we visited and left in operating conditions apparently did not make any observations, or fewer than expected, despite the availability of supplies or personnel. Some of the problems encountered were not entirely technical in nature. Fig. 2. The NAMMA radiosonde and pilot balloon network, showing which sites made

observations and those that apparently did not.

Fig. 1 In all, 385 pilot balloon observations have been received to date. This was considerably short of our expectations.

Summary

Failures•Gas supplies were unreliable throughout the region, complicating station operations; only partial solutions to these problems were fouond during NAMMA. •Protocol problems and gas supply issues prevented any observations being made from Senegal, despite a major effort there to arrange for the operation of four pilot balloon stations.•One Mali site was discovered to be abandoned, but only after a lengthy visit to the site.

ConclusionsAcknowledgements1. Observations will provide modest help in improving upstream continuity of tropical waves existing Africa

during NAMMA.2. Our NAMMA effort provides a reality-check for any future activity related to studies of easterly waves

over Africa. We found that the current pilot balloon station network is mostly abandoned and poorly functioning in may countries in the region. There are many reasons for this. Much longer lead times are needed for any land-based future activity - a minimum of 1 year (instead of the 3 months available during NAMMA). Finally, the basic infrastructure and personnel problems in West African Meteorological Services must be dealt with to realistically expect routine monitoring from enhanced sounding network on this region.

Funding for this work has been provided

by the Atmospheric Dynamics section of

NASA. The logistical support of the

NAMMA community is gratefully

acknowledged.

NOUADHIBOU

AUGUST

SEPTEMBER

Successes•Pilot balloon observations from Mauritanian sites should be useful for describing dust outbreaks and wave passages at higher latitudes (~16°-20° N).•Two Mali sites, making twice-daily soundings at 06Z and 18Z, functioned for about 50 days.•Guinean radiosonde site (Conakry) provided some overlap with NAMMA aircraft observational phase.

Our group traveled to Dakar, Senegal on July 10th to determine the current status of the sounding network, establish the Senegalese component first, and then travel to the

surrounding countries.

Because of the mis-shipment of materials to Senegal, travel to the other countries in the region was delayed. After visiting Mali and splitting to visit the widely separated sites at

Mopti and Kayes, the team returned to Senegal. Splitting again in early August, one group traveled to Guinea and the other to Mauritania. In addition, permission to establish the

observations and travel to the stations within Senegal (4 sites, including Dakar) was also delayed due to some protocol mistakes. Although all Senegalese sites were visited by

August 8th and procedures seemingly worked out (the observers had been trained and theodolites replaced) no observations seemingly were made at any of the sites.

Establishing stations

Above, left: Histogram of number of observations reaching different levels at Bamako. The rapid decline in the number of observations between 1700 and 1800m AGL is due to the common practice of ending tracking of the balloon 10 minutes after launch. This is especially obvious in early morning (before sunrise) launches, but present also in afternoon launches. Disturbingly, the highest sounding was made during the observer training session--the following 101 observations were tracked to lesser altitudes. Fortunately, other stations do not seem to show this characteristic. Right:

Left: Comparison of Bamako radiosonde

winds (twice daily at 00Z and 12Z) and

pilot balloon winds (06Z and 18Z). Note

the good agreement before August 27th--

but poor thereafter. Source of this

discrepancy unclear, but possibly related

to observer change.

In maps above, note the value of the pilot balloon data in confirming the radiosonde winds. Bamako and Nouakchott pibal winds not plotted.

Left: Time-height sections of the wind from pilot balloon observations at

Nouadhibou, Mauritania. This site provided the most complete data overall of

any pibal site during NAMMA.