PIURA VHF RADAR

The Piura VHF radar (7o N dip latitude) was constructed in 1989 by the National Oceanic and Atmospheric Administration’s Aeronomy Laboratory, the Cooperative Institute for Research in Environmental Sciences of the University of Colorado, and two Peruvian Institutions: the Universidad de Piura and the Instituto Geofísico del Perú. The Piura radar constitutes the easternmost element of a series of atmospheric radars located close to the geographic equator in the Pacific Ocean sector. The main purpose of this radar is to study the lower atmospheric dynamics operating as a wind profiler. Coincidentally, one of its predefined beam positions points perpendicularly to the magnetic field.

Since 1991, we have conducted intermittent ionospheric experiments until 1999. Preliminary results based on these observations can be found in Woodman et al., [1999] and Chau and Woodman [1999]. Since January 2000 we have been getting “continuous” measurements of E region irregularities. The statistics of these measurements have been submitted to Annales Geophysicae [ Chau et al., 2001 ]. Among other important results that we have found: (1) the E region irregularities resemble more the midlatitude irregularities than the equatorial ones, (2) the E region echoes are stronger and occur more during the local summer (December-March), (3) the weaker echoes and less occurrence are accompanied by strong Northward winds, (4) we might be able to use the Doppler velocities from those irregularities to measure the meridional winds at those heights (95-110 km).

In addition, by conducting simultaneous F region measurements at both Jicamarca and Piura, we have observed that the seasonal and daily occurrences of Piura F region irregularities is similar to the occurrence of topside equatorial spread F (ESF) irregularities over Jicamarca. So far only topside F region irregularities have been observed over Piura. The likelihood of occurrence of F region irregularities over Piura and therefore topside ESF over Jicamarca is greater when there are no E region irregularities over Piura. On the other hand, there is more probability to observe bottom type/bottom side ESF irregularities over Jicamarca when their E region irregularities are observed over Piura. However, we have not taken into account events that occur when there is no spread F season.

In addition to these general statistical characteristics, we are planning to conduct radar imaging experiments at Piura similar to those conducted at Jicamarca [e.g., Hysell and Chau, 2001] in order to get a better understanding of these echoes. The receiving antennas have been already constructed and installed. Preliminary experiments were conducted last August although we obtained only a few hours of reasonable data. At that time we experienced a strong interference and there were weaker and fewer echoes as expected from our statistics. We expect to conduct new experiments this coming summer when the echoes are expected to be stronger and to occur more frequently with an improved acquisition system.