Source
https://niwa.co.nz/climate-and-weather/regional-climatologies/nelson-and-tasman — original source (opens in a new tab; the file is not redistributed)
NIWA — The Climate and Weather of Nelson and Tasman, 2nd ed (Macara 2016)
Primary regional climatology — NIWA Science & Technology Series No. 71
G. R. Macara (2016), 2nd edition; normals computed over the 1981–2010 standard 30-year period (underlying data: NIWA National Climate Database / CliFlo, HIRDS). A ~60-page report (text + data tables), not a raw dataset. The authoritative primary climatology for the Lower Moutere / Waimea / Nelson pilot region. Tables report selected named stations (Nelson, Motueka, Takaka, Murchison, Farewell Spit, St Arnaud) — Nelson and Motueka are the nearest proxies for the Waimea/Moutere lowland, not a Lower Moutere station. Gives mean daily global solar radiation (MJ/m²/day), not PV specific yield — the yield conversion sits in CR_010. 1981–2010 normals: a baseline, not a climate-change-adjusted forward projection.
Summary
NIWA’s authoritative regional climatology for Nelson City and Tasman District, 2nd edition (Macara 2016, NIWA Science and Technology Series No. 71), with normals over the 1981–2010 standard period. The region is the most north-westerly part of the South Island — well-exposed to weather from the north, sheltered from the south. The Nelson and Waimea Plain lowlands are the driest, sunniest, mildest, and least windy parts: Nelson records ~959 mm annual rainfall and is among the sunniest places in New Zealand (~2,400 sunshine hours), while the Tasman Mountains exceed 6,000 mm. For Neobiome Intelligence this is the primary-source regional input layer for the Lower Moutere / Tasman pilot — solar radiation, heating degree-days, wind, rainfall, dry-spell frequency, soil-moisture deficit, and frost given by named station and table. It resolves RT_102, the Macara (2016) reference previously cited only second-hand inside CR_010. OT_030
Key claims
- claim: "Nelson mean daily global solar radiation: annual 15.2 MJ/m²/day (January peak 24.4, June minimum 6.0); Motueka annual 15.1, Takaka 15.2. Nelson ~2,400 annual sunshine hours, frequently top-four sunniest in NZ. (Solar radiation observations >10 years exist for only three regional sites: Motueka, Nelson, Takaka.)"
source_location: "Table 19, p28; Summary p6; Figure 16, p27"
- claim: "Winter solar suppression: inland Tasman winter anticyclones support low cloud/fog 'chiefly during May to September'; Nelson Airport averages 17 fog days/year, of which 60% (10 days) fall May–August. The '3–5 consecutive days' figure is a CR_010 characterisation, not a tabulated value in Macara 2016."
source_location: "Typical Weather Situations p9; Fog § p29, Table 20"
- claim: "Mean annual heating degree-days (base 18°C): Nelson 2,108, Motueka 2,078, Takaka 2,018, Murchison 2,266, Farewell Spit 1,594, St Arnaud 3,224; Nelson HDD peaks July 346 / August 310. Cooling degree-days minor (Nelson annual CDD 56)."
source_location: "Table 26, p35"
- claim: "Mean annual wind speed (km/hr): Farewell Spit 21.2 (exposed coastal, windiest), Nelson 11.7, St Arnaud 7.6, Murchison 7.2, Motueka 5.0 (most sheltered). Strong-wind days (daily mean >30 km/hr): Nelson 30/yr, Motueka 2, St Arnaud 0.6, Murchison 0. Nelson diurnal peak ~1500 hrs (19.5 km/hr), overnight low ~0600 hrs (7.2 km/hr)."
source_location: "Tables 1–3, pp13–14"
- claim: "Annual rainfall normal (1981–2010): Nelson 959 mm, Motueka 1,341, Takaka 2,012, Collingwood 3,371; Tasman Mountains exceed 6,000 mm. Rainfall fairly even through the year, Feb–Mar driest. Dry spells (≥15 consecutive days <1 mm/day): Nelson one every 4 months (mean 20, max 40 days, 13 May–21 Jun 2008); Takaka one every 6 months; most frequent in summer (Nelson 34%, Takaka 36%)."
source_location: "Table 6 p16; Tables 12–13 p20; Summary p6"
- claim: "Mean annual soil-moisture deficit (150 mm soil capacity): Nelson 317 mm (highest tabulated; 90 mm in January alone), Motueka 250, Takaka 124, Matakitaki 53. Penman annual potential evapotranspiration: Nelson 901 mm, Motueka 817 mm. Summer soil-moisture deficit at Nelson means irrigation is necessary to maintain plant growth."
source_location: "Table 23 p33; Table 24 p34"
- claim: "Nelson/Tasman afternoon temperatures typically 20–23°C in summer, overnight −1 to 5°C in winter; low-elevation median annual temperature 11–13°C. Days/year with minimum air temperature <0°C: Nelson 31, Motueka 32, St Arnaud 87, Lake Rotoroa 60, Farewell Spit 0.5. Highest recorded Murchison 36.8°C (2005); lowest St Arnaud −10.1°C (2011). Coastal Nelson/Tasman is mild with maritime moderation; frost is more frequent inland."
source_location: "Air temperature § p22; Table 16, p25"Neobiome Intelligence relevance
Primary-source regional climate inputs for the Lower Moutere / Tasman pilot. Nelson and Motueka are the nearest tabulated station proxies for the Waimea/Moutere lowland. It supplies, from named tables, the upstream resource inputs behind several pilot figures already in the wiki — corroborating, not duplicating, them.
- D01 (energy): solar radiation (Nelson 15.2 MJ/m²/day annual, 24.4 Jan / 6.0 Jun) is the upstream supply input behind CR_010’s specific-yield figures, and the ~25% June/January ratio is the physical basis for the winter-solar swing and why off-grid winter coverage isn’t battery-economic at 41°S. Heating degree-days (Nelson 2,108, base 18°C) corroborate the CR_015 pilot space-heat load and the case for biomass/heat-pump heating per Interview I [INT_001]. Low inland wind (Motueka 5.0 km/hr) corroborates CR_013’s low pilot CF — small wind is viable only on exposed coast (Farewell Spit class). Winter fog (60% of Nelson fog days May–Aug) is the primary justification for not battery-sizing to full winter solar coverage. OT_030
- D03 (water): rainfall (Nelson 959 mm/yr — the driest part of the region) fills the pilot ②
rainfall_mm(rainwater catchment yield); national 16-region rainfall remains RT_142. Dry-spell frequency (Nelson one every 4 months, max 40 days) sets the rainwater-harvesting buffer requirement, and summer soil-moisture deficit (Nelson 317 mm/yr, PET 901 mm) flags that irrigation is necessary for food self-sufficiency in the driest months — sizing the veg→water irrigation coupling. OT_030
Caveats for NI use: named-station proxies (Nelson/Motueka), not a Lower Moutere gauge; mean daily global solar radiation (MJ/m²/day), not PV specific yield (that conversion is CR_010’s); 1981–2010 normals, so post-period climate-change drift is not captured — a baseline, not a projection. The widely reused “3–5 consecutive-day winter fog” figure is CR_010’s characterisation, not a tabulated value here.
Research targets
Documents to retrieve
- None — this is itself the primary NIWA regional climatology; the underlying NIWA databases (CliFlo, HIRDS) are query tools rather than ingestable documents.
Research gaps
- A Lower Moutere / Waimea-specific station record (rather than the Nelson and Motueka proxies tabulated here) would tighten the pilot inputs; NIWA CliFlo (cliflo.niwa.co.nz) holds station-level data if a closer gauge exists.
- Confirm CR_010’s PV specific-yield (kWh/kWp) traces to this report’s radiation table plus a documented conversion method, not an independent unstated assumption — OT_030 supplies the radiation resource (MJ/m²/day), not the yield itself.
Connections
Links to
Referenced by
EDT domains (2): D01: Renewable Energy & Storage Systems · D03: Water, Waste & Circular Systems
Sources (1): OT_036