Introduction Trip report Description of Kaashidhoo
INDOEX observatory and tower Description of Hulule and Male General information


Maldives Site Survey - Selection of INDOEX Observatory Site

Trip Report

Between 07 July and 17 July 1997, a team consisting of J.M. Lobert, H. Nguyen, and V. Ramanathan went to the Republic of the Maldives to select surface observation sites for both long-term and intensive field operations during INDOEX. This document is a detailed description of the tentative choice of locations, which is awaiting official approval by the INDOEX plenary meeting in September 1997, in La Jolla, CA. Two islands were chosen for ground-based operations: Hulule, the airport island, for LIDAR, some radiometric and meterorlogical operations, and Kaashidhoo for most of the radiometric and all of the trace gas and aerosol measurements.

The site survey delegation in front of the proposed observatory location on Kaashidhoo (left to right): Mr. Abdul Rauf (island chief of Thulusdhoo), Mahmood Riyaz (Assistant Environmental Analyst of MPHRE, our local contact person), Abdullahi Majeed (Deputy Minister of MPHRE), Muhamed Adam (Kaafu Atoll Chief), V. Ramanathan (C4 director), Jürgen M. Lobert (C4 project scientist), Hussain Moosa (Kaashidhoo island chief), and Hung Nguyen (C4 deputy director).

The 10-day expedition was used to visit twelve islands in the North Male (Kaafu) Atoll, eight of which were tourist resorts, four were native islands (Table 1). The airport island Hulule was selected meteorological and LIDAR operations as well as some possible radiometric instruments. For the trace gas and aerosol measurements, Hulule is not suitable due to its pollution from aircraft, frequent ship traffic and, most importantly, its proximity (~1 km) to Male, the capital of the Maldives. For those measurements, only tourist resorts were considered initially, based on the assumption that power requirements would be too demanding for native islands. It turned out that this is not necessarily true and that native islands have certain advantages over tourist resorts, whose managers/owners were generally concerned about the impact of our measurements, and particularly a tower for radiometric observations, on the resort’s idyllic surrounding. However, not many native islands were suitable, either, mostly due to their location or geographical orientation.

Table 1: List of islands that were considered for INDOEX operations.






Capital, large ships will dock here, no space for instruments



selected for met ops and LIDARs


Emboodhoo Finholhu

resort island

distant 3rd choice, too close to Male and Hulule


resort island

previous 1st choice, under construction for 1 year, vehicles


resort island

2nd choice, furthest north in Male atoll


resort island

under heavy construction throughout the next year

Kuda Huraa

resort island

exclusion sectors too large


resort island

not enough power available, v. small island


resort island

no clean point on the island, cars, power house


resort island

4th choice, water units, too close to local impact



native island

clean NE sector, but exclusion sector too large


native island

#1 choice for INDOEX site (radiometric, trace gas, aerosols)

The distribution of islands in the North Male Atoll and their impact on each other’s air quality made it difficult to find sites that are suitable for trace gas and aerosol measurements. Every inhabited island needs to be viewed as a potential contamination source and has its own inevitable local pollution source in form of a power house. Islands that operate any type of vehicle were automatically excluded from the survey. Very few islands are far enough away from other islands to neglect their respective emissions and most of the resorts with easy logistics (= proximity to Male/Hulule) are lined up on the east side of the atoll (Figure 1), creating large exclusion sectors with local pollution in the NE and SW.

Figure 1: (a) An overview of the central Maldives. These atolls are located in the center of the Maldivian island chain. There are no other atolls to the east or west other than the two parallel rows of atolls shown. The Maldives stretch further north to about 7.1Ý N and further south to about 1Ý S. Resort names are shown in red, native islands in white, the light shading indicates the clean air sectors. The inset map shows the INDOEX operation area with ground stations on Mauritius, Reunion, Minicoy and Kaashidhoo highlighted in yellow.

(b) A photo of the North Male Atolls taken from space with the location of Kaashidhoo, Hulule and Male indicated.

Radiometric measurements can be carried out without consideration of local air pollution. For trace gas and aerosol measurements, however, local pollution from power houses, vehicles, cooking, burning etc. needed to be considered. As the NE monsoon will be the focus of INDOEX, the highest priority was given to locally-clean air sectors in the north-east with less emphasis on clean air from the south-west (SW monsoon) and year-round clean air from all directions. The two sectors without local pollution are shown in Figure 1a as a white highlight.

A wind analysis of the years 1980 to 1995, carried out by Mr. Mahmood Riyaz from the Ministry of Planning, Human Resources & Environment (MPHRE) of the Maldives, shows two distinctively different winds throughout the year. NE monsoon winds center around 60° ± 30° and SW monsoon winds appear to be mostly due west to WNW around 280° ± 30° with the SSE direction having the lowest frequency of winds (Figure 2).

Figure 2a: Analysis of wind direction in Male. The two prevalent wind directions are north-east and due west.

A previous visit of the Maldives concluded that Meerufenfushi (Meeru) would be the primary choice for atmospheric measurements. Meeru is located on the east flank of the atoll and also the second furthest east point in the entire Maldives (Figure 1). It shows the largest clean sector to the NE (~355° to 170°) of all islands near Male, is not too far away from the project base and does not have too much, but some contamination in a 50 km radius. The island itself is north-south aligned with the power house in the south (creating an exclusion sector of about 170° to 240°). Meeru is a tourist resort with currently 214 rooms (428 occupancy) and close to 100 staff.

Figure 2b: Rainfall record of Male. Data are means from a 29 year record.

During our recent visit, we found out that the resort is unfortunately planning on some major changes on the island, which involves construction of 60 new rooms, 3 new restaurants and a helicopter pad in the NE corner, which would have been our prime spot for measurements. Construction will last for about one year and involves biomass burning, diesel fumes from construction vehicles and heavy mineral dust.

Only one other island in the main Kaafu atoll was found to be a suitable replacement for Meeru. Helengeli, another resort, is located further west than Meeru, but also further north and away from Male and Hulule. The island is SW-NE aligned and a spot on the NE corner in the staff area would have been our primary target for setting up an observation site. Strong concerns were expressed by the managers regarding impact on their tourist operation.

When the INDOEX delegation met with the Maldivian officals, deputy director of MPHRE, Mr. Mohamed Khaleel and deputy minister of MPHRE, Dr. Abdullahi Majeed, it was suggested to consult the minister of MPHRE, Mr. Abdul Rasheed Hussain, regarding the site selection process. Despite the fact that the ministry is theoretically capable of forcing our operation on resort owners, we did not want such action to occur, as it would have likely created problems in local support and maintenance. Furthermore, the minister made very clear that it was the wish of the ministry and the president of the Maldives to accommodate the INDOEX ground-based operation on a native island rather than a resort.

With this new direction, only two islands were left to choose from. Thulusdhoo, Kaafu’s administrative island, and Kaashidhoo, a single-island atoll at the northern end of Kaafu (Figure 1). We had visited Thulusdhoo before and kept it in mind as an alternative to Kaashidhoo, which was the minister’s suggestion. The minister also assured us that there would be no space limitations and concerns with respect to tower and other structures on any native island. Upon visiting Kaashidhoo, the delegation quickly realized that this was, indeed, a primary location for the INDOEX observatory.

Next section: Description of Kaashidhoo

C4 - 25 August, 1997