Field Definitions are Available Here
Collection
varstring(50)
Mandatory if applicable
Keyword used to describe the general topic area of the collection. A collection can conceivably cover several topics.
Cryosphere
ECSDisciplineKeyword, ECSTermKeyword, ECSVariableKeyword, ECSParameterKeyword
Cryosphere
Must be used with ECSDisciplineKeyword, ECSTopicKeyword, ECSTermKeyword.
METADATA > COLLECTIONMETADATA > DisciplineTopicParameters > DisciplineTopicParametersContainer.ECSTopicKeyword
/gmi:MI_Metadata/gmd:identificationInfo/gmd:MD_DataIdentification/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:keyword/gco:CharacterString
Note: if used, see also - /gmi:MI_Metadata/gmd:identificationInfo/gmd:MD_DataIdentification/gmd:descriptiveKeywords/gmd:MD_Keywords/gmd:type/gmd:MD_KeywordTypeCode
Descriptive Information