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The average ground type within a grid box is not necessarily representative of an individual location. Land surface characteristics can be very variable within a grid box. Users and forecasters should take into account the peculiarities of a location when interpreting model output.
Representation of an urban or city surface was introduced in Cy49r1 in autumn 2024. Extensive concrete and buildings may possibly provide a source of heat (the heat island effect) and even moisture (from air-conditioning units).
The slope and aspect of orography within each grid box (e.g. south-facing, steepness) is not taken into account and HTESSEL may consequently under- or over-estimate solar heating and runoff.
an urban tile models the fluxes of heat, moisture and momentum at the surface and allows a more realistic representation the heat island effects of towns and cities.
separation of tiles into high and low vegetation gives a more accurate seasonal variability of vegetation and incorporates the differing albedo effects of underlying snow cover

Vegetation type	Assigned vegetation height	Assigned vegetation coverage	Vegetation type	Assigned vegetation height	Assigned vegetation coverage

Evergreen needle leaf trees	H	0.90	Bogs and marshes	L	0.60
Deciduous needle leaf trees	H	0.90	Water and land mixtures	L	0.60
Evergreen broad leaf trees	H	0.90
Deciduous broad leaf trees	H	0.90	Tundra	L	0.50
Mixed forest / woodland	H	0.90	Semi-desert	L	0.10
Interrupted forest	H	0.90	Desert	–	–

Irrigated crops	L	0.90	Urban	-	-
Crops, mixed farming	L	0.90
Short grass	L	0.85
Tall grass	L	0.70	Ice caps and glaciers	–	–
Evergreen shrubs	L	0.50	Inland water	–	–
Deciduous shrubs	L	0.50	Ocean	–	–

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