Especially
Particularly, Additionally, Unusually
adverb
The kanji and the word are exactly the same. That means they share meanings as well.
This is the kanji followed by the particle に, so it uses the kun'yomi reading like a kanji does if it's alone. You haven't learned this reading yet, so here's a mnemonic to help you:
What do you wear when it's especially cold out? Your favorite coat (こと). You only wear it when it's unusually cold though, never any other time.
殊に、来年はコウイチ様生誕100周年を記念するメモリアル・イヤーとなります。
Additionally, next year will be the memorial year commemorating the one hundredth year anniversary of Koichi-sama’s birth.