Extended dry periods

Extended dry periods are stretches without meaningful rain, during which dust settles on module glass and is not washed away. The dust cuts glass transmittance and lowers array current, so less light reaches the cells while the plant stays online. This drives granular dust soiling losses. In the field this shows up as a gradual drop in irradiance-normalized production through the dry period, often followed by partial or full recovery after real rain or washing. Nearby roads, exposed soil, farming, construction, prevailing wind and row edges can make the loss uneven across the site. To diagnose it, look for dry periods where output falls without availability, clipping, curtailment or irradiance sensor problems. Then compare against soiling stations, rainfall, cleaning logs and reference blocks. Exposure is reduced by cleaning: in wet tropical climates weekly cleaning is recommended during dry spells, adjusted to how fast dust builds up. Cleaning triggers should be set by the value of the lost energy, using a soiling model calibrated with operational data.

<!-- review notes

• sentence 1: support check: partial - Passages say dust accumulates during dry periods and recovery follows meaningful rain, but don't define dry periods or explicitly say dust settles and isn't washed away.
• sentence 6: support check: partial - Table says weekly cleaning is recommended during dry spells in wet tropical climates, adjustable by dust intensity, but the framing as exposure reduction is generic and the table says nothing explicit beyond that. -->